Proper scaling of statespace models is important for accurate computations. The fem model of the example chosen for this paper actually ignored. Modal assurance criterion mac file exchange matlab central. Other areas are treated in a general sense to introduce their elementary concepts and relationships to one another. The modal assurance criterion mac introduced in 23. The modal assurance criterion that survives today is what was originally identified as big mac. Correlation of mode shapes, the coordinate modal assurance criterion. The output, frf, is an h1 estimate computed using welchs method with window to window the signals. How can i compute the modal assurance criterion of. All treated theory is implemented in matlab code and these scripts are extensively explained. Modal assurance criterion mac file exchange matlab. If you do get unwanted wrap around of stuff shifting in, then you can use assignment, but i think circshift will be the simplest way.
Analysis of compliance maps with matlab toolbox diva. In the modal analysis of plane frames the main aim is to determine the natural mode shapes and frequencies of an object or structure during free vibration. Criterion behaviour which focuses only on the eigen values and eigen. Contributed by the design engineering division of asme for publication in the j ournal of c omputational and n onlinear d ynamics. Projected coordinate reference systems control transformation from geographic to map coordinates to represent a curved surface such as the earth in two dimensions, you must geometrically transform literally, and in the mathematical sense, map that surface to a plane. Some of the other assurance criteria that will be discussed include the coordinate modal assurance criterion comac, the frequency response assurance criterion frac, coordinate orthogonality. Improved modal assurance criterion using a quantification.
Id probably just use circshift in your case, since you dont seem to have to worry about stuff getting shifted in. If x or y is a matrix, each column represents a signal. Spatial correlation of mode shapes, the coordinate modal. In a camerabased coordinate system, the points are defined relative to the center of the camera. The development of the mac was modeled after the development of the ordinary coherence calculation associated with computation of the frequency response function. This function is to compute and plot modal assurance criterion mac matrix. Use the coordinate system blocks to standardize units across your model, transform spatial representations and coordinate systems, describe the behavior of three and sixdegreesofmotion bodies. Taking the classical modal assurance criterion mac, the need to diagnose. The modal assurance criterion twenty years of use and abuse. The array is stationary and is located 150 meters in the zdirection from the transmitting array. Use the coordinate system blocks to standardize units across your model, transform spatial representations and coordinate systems, describe the behavior of three and sixdegreesofmotion bodies, and perform common aerospace math operations. A numerical example and a benchmark study with experimental data are presented to show the advantages of the proposed energybased criterion in comparison to the traditional modal assurance criterion. Modal assurance criterion one of the most popular tools for the quantitative comparison of modal vectors is the modal assurance criterion mac.
Spatial correlation of modeshapes, the coordinate modal assurance criterion. Navigation coordinates are defined with respect to the center and surface of the earth. Modal assurance criterion the modal assurance criterion analysis mac analysis is used to determine the similarity of two mode shapes. Modal analysis on an exhaust manifold to define a catalyst fe. Latitude and longitude specify the position of a point on the surface of a planet. They are defined as angles between the point, the equator, and the axis of rotation. Modal analysis on an exhaust manifold to define a catalyst. Modal analysis is defined as the study of the dynamic characteristics of a mechanical structure.
Moreover, the natural frequencies which provide the global information of the structure are used to guarantee the accuracy of modal properties of the global model. When you reconstruct a 3d scene, you can define the resulting 3d points in one of two coordinate systems. Modal analysis of plane frames national institute of. Xmodal experimental modal analysis software structual. Taking the classical modal assurance criterion mac, the need to diagnose sensors contributing to poor correlation was identi. Modeling aerospace trajectories requires positioning and orienting the aircraft or spacecraft with respect to the rotating earth. A new section has been added to the manual, containing verification examples. The dynamic analysis of frames requires inclusion of axial effect in the stiffness and mass matrices. Robotics system toolbox provides functions for transforming coordinates and units into the format required for your applications. The coordinate strain modal assurance criterion is developed to evaluate the correlation level at each coordinate over the experimental and the analytical strain mode shapes. Matlab implementation of an operational modal analysis. Global and local coordinate systems radar example matlab.
Coordinate transformations and trajectories matlab. Structural dynamics teaching example abravibe main page. Citeseerx scientific documents that cite the following paper. To learn more about the different coordinate systems, see coordinate transformations in robotics. We provide functions to compute modal assurance criteria mac and orthogonality, generate rigid body mode shapes from supplied finite element model geometry, generate a modal substructure from mode shapes, compute normal, complex, and multivariate mode indicator functions, and synthesize frequency response functions frf from real normal modes.
I have some problems in understanding criteria of computing mac. Ewins, spatial correlation of modeshapes, the coordinate modal assurance criterion. Structural dynamics teaching example a linear test analysis. Use the coordinate system functions to standardize units across your model, transform spatial representations and coordinate systems, describe the behavior of three and sixdegreesofmotion bodies, and perform common aerospace math operations. How can i compute the modal assurance criterion of experimental mode and fe mode shape. Coordinate modal assurance criteria comac this method helps you identify the location of systematic differences between the two result sets. You clicked a link that corresponds to this matlab command. If the author is still active, i highly recommend he add some sort of tutorial or at. Spatial correlation of mode shapes, the coordinate modal assurance criterion. The modal assurance criterion mac is the most widely used criterion for vector correlation mainly because of its simplicity. In the internal development of the modal assurance criterion at the university of cincinnati, structural dynamics research lab ucsdrl, a little modal assurance criterion little mac1, a big modal assurance criterion big mac and a multiple modal assurance criterion multimac3 were formulated as part of the original development.
Towards solving large scale topology optimization problems. If designer could extract the modal parameters with as high accuracy as with traditional modal analysis without measuring the input force, it will decrease the project cost as well as analysis time. The aerospace toolbox coordinate systems are based on these underlying concepts from geodesy, astronomy, and physics. Little mac and multimac were primarily testing methods and are not discussed further here. For more information on the spatial coordinate system, see spatial coordinates image processing toolbox. Fundamental coordinate system concepts coordinate systems allow you to track an aircraft or spacecraft position and orientation in space. Multiobjective model updating optimization considering. A graphical method of comparison was found for simple structures, which considers the spatial distribution of the entire frequency response spectrum. In appendix c a manual is written in which the entire pro. Coordinate systems are an important part of aerospace systems. A numerical example and a benchmark study with experimental data are presented to show the advantages of the proposed energybased criterion in comparison to the. Xmodal iii can utilize data acquired from any data acquisition system as long as the datacan be provided in universal file uf format or a documented matlab data format. Structural dynamics teaching example a linear test. The received signal strength in any direction is a function of the incident angle of the signal in the local array coordinate system.
The validity of such a tuning procedure can be assessed by computing the modal assurance criterion mac 40 step 2. Ecomac enhanced coordinate modal assurance criterion. Regionbased decomposition, stableunstable decomposition. Pdf improved modal assurance criterion using a quantification of. Crossorthogonality 1 the cross orthogonality method is similar to mac. Pdf scanning laser vibrometer measurements generate detailed maps of modal. Frequencyresponse functions for modal analysis matlab. Coordinate reference systems provide a framework for defining realworld locations. Introduction to operational modal analysis request pdf. Load a file containing a high modal density frequencyresponse measurement. Improved modal assurance criterion using a quantification of.
Xmodal iii provides a graphical user interface gui in parallel with a command driven interface to provide users with any type of programmatic interaction desired. The output, frf, is an h 1 estimate computed using welchs method with window to window the signals. Coordinate transformation can also be useful for scaling poorlyconditioned models. Comparative study of model correlation methods with. Use the coordinate system functions to standardize units across your model, transform spatial representations and coordinate systems, describe the behavior of three and sixdegreesofmotion bodies. Run the command by entering it in the matlab command window.
Frequencyresponse functions for modal analysis matlab modalfrf. Point compliances represented by a color scale are. The data corresponds to an unstable process maintained at equilibrium using feedback control. Ojeda bachelor of science in electrical science and engineering, mit, 2010 master of engineering in electrical engineering and computer science, mit, 2011.
Modal assurance criteria mac modal assurance criteria quantitatively compare all possible combinations of mode shape pairs. An example of a poorly scaled model is a dynamic system with two states in the state vector that have units of light years and millimeters. It thus becomes possible to provide improved modal assurance criterion. You can also generate trajectories using polynomial equations, bsplines, rotation matrices, homogeneous. Data is represented using either a geographic coordinate system latitudelongitude or a projected coordinate system xy.
Store the data as an idfrd object for identification. The function for computing the modal assurance criterion mac values has. The receiving array is also a 5by5 ura composed of isotropic antenna elements. Modal analysis of active flexible multibody systems request pdf. Matlab implementation of an operational modal analysis technique for vibrationbased structural health monitoring by alejandro p. This application note emphasizes experimental modal techniques, specifically the method known as frequency response function testing. The most obvious example of this situation would be when a relatively.
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