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==First steps==


===Modal software first description===


When you launch Modal, the following window appears few seconds.
[[Image:Modal_Manual_16.gif|framed|none]]
Finally the following window is displayed
[[Image:Modal_Manual_17.png|framed|none]]
Click on <nowiki>’</nowiki>file<nowiki>’</nowiki> in the menu toolbar and on <nowiki>’</nowiki>open workspace<nowiki>’</nowiki>.
For the first time you can open one of existing projects installed at the same time than the software in the directory <nowiki>’</nowiki>examples<nowiki>’</nowiki>.
There are:
- 4 different projects for Experimental Modal Analysis
- 2 different projects for Operational Modal Analysis
[[Image:Modal_Manual_18.png|framed|none]]
[[Image:Modal_Manual_19.png|framed|none]]
The main interface of the software is so displayed.
The window is shared in four distinct parts. Each of them has their own utilities.
[[Image:Modal_Manual_20.png|framed|none]]
'''Workspace panel''' contains:
## an operation tree organized as a wizard to follow the different steps of a modal analysis
## a data tree where you can fine all the data and results imported or calculated in the opened project.
'''Activated window''' can display:
## 2D windows: time domain data, FRFs estimation, curve-fitting…
## 3D windows: geometry, mode shapes.
'''Output Panel''' displays the last calculated results.
'''Control Panel''' contains the different commands and functions respectively useful for 2D and 3D windows.
===To know more===
To discover the different function of this software, please open the <nowiki>’</nowiki>getting started<nowiki>’</nowiki> file installed at the same time than the software. You can follow the different steps described in the document to obtain some results very quickly.
The online help embedded within the software can help you and be also consulted for all kind of questions.
==Environment==
===General interface===
When Modal is running, the following interface will be displayed.
[[Image:Modal_Manual_26.png|framed|none]]
The menus, toolbars, workspace panel, output panel and control panel are listed from top to bottom. The center empty area of the interface is reserved for the main window. The workspace panel, output panel and control panel are generally called shortcut panels. The state bar locates in the bottom of window. The menus<nowiki>’</nowiki> tips, processing bar and its tips are all showed on the state bar.
When you create a new configuration file or open a workspace file without measurement data, the <nowiki>’</nowiki>Config<nowiki>’</nowiki> window will first be shown.
[[Image:Modal_Manual_27.png|framed|none]]
When users open a configuration file or workspace file with measurement data, the <nowiki>’</nowiki>Output<nowiki>’</nowiki> curve window will first be shown. There are two cursors on the left and right of the window respectively. The red point denotes the closest point to the cursor. The X and Y axes values of the two red points are shown dynamically on the top right corner of the window.
[[Image:Modal_Manual_28.png|framed|none]]
Each part of the interface can be shown or hidden through menu or toolbar operation. Users can also change the size or positions of each part by dragging the mouse.
[[Image:Modal_Manual_29.gif|framed|none]]
Besides, all parts of the interface can be arranged to floating style for the purpose of getting more display space.
[[Image:Modal_Manual_30.png|framed|none]]
The software can also remember the adjusted interface style automatically in order to fit users<nowiki>’</nowiki> habits.
==Geometry modelling==
===Principle===
To begin with the geometry modeling, we should know about three important concepts, i.e. coordinates, nodes and links. A geometry is made up of these three elements.
====Coordinates====
=====Global and local coordinates=====
There are two kinds of coordinate systems in Modal, i.e. the global coordinate system and local coordinate system. The global coordinate system which defines the global origin point and global X, Y, and Z axis, is a kind of Cartesian coordinate. The No. of global coordinate system is 0 in Modal. The local coordinate systems are all defined referring to the global coordinate. Three kinds of local coordinate systems are available now, i.e. the Cartesian coordinate, the cylindrical coordinate and the spherical coordinate. You can have only one global coordinate, but many local coordinates. All the coordinates in Modal are defined according to the right-hand rule.
=====Cartesian coordinate=====
To define a point in the Cartesian coordinate system, you need three translations x, y, and z as the following:
[[Image:Modal_Manual_31.png|framed|none]]
=====Cylindrical coordinate=====
To define a point in the Cylindrical coordinate system, you need radius x, rotation y, and translation z, as the following:
[[Image:Modal_Manual_32.png|framed|none]]
=====Spherical coordinate=====
To define a point in the Spherical coordinate system, you need radius x, rotation y, and rotation z, as the following:
[[Image:Modal_Manual_33.png|framed|none]]
It<nowiki>’</nowiki>s easy to transform between these three coordinate systems.
=====Define a coordinate=====
[[Image:Modal_Manual_34.png|framed|none]]
To define a local coordinate system, you should assign an ID No., select the coordinate type, and specify the position and direction of local coordinate frame. A local coordinate'' O''<sub>''L''</sub>''X''<sub>''L''</sub>''Y''<sub>''L''</sub>''Z''<sub>''L ''</sub>is always defined referring to the global coordinate ''OXYZ''. In Modal, three points are employed to specify the coordinate frame, i.e. the original point ''P''<sub>1</sub>, a point ''P''<sub>2</sub>'' ''on the ''X''<sub>''L''</sub> aix, and another point ''P''<sub>3'' ''</sub>on the ''X''<sub>''L''</sub>''Z''<sub>''L''</sub> plane. For convenience, the point ''P''<sub>3 </sub>is usually selected on the local ''Z''<sub>''L ''</sub>axis.
[[Image:Modal_Manual_35.png|framed|none]]
As shown in the above picture: the local ''X''<sub>''L''</sub> axis can be determined by ''P''<sub>1</sub> and ''P''<sub>2</sub>; the plane ''X''<sub>''L''</sub>-''Z''<sub>''L''</sub> can be determined by ''P''<sub>1</sub>, ''P''<sub>2</sub>, and ''P''<sub>3</sub>, thus the ''Z''<sub>''L ''</sub>axis can also be obtained; the ''Y''<sub>''L ''</sub>axis can then be determined according to the right-hand rule.
You can also define a local coordinate system by the origin point and three Euler angles.
====Nodes====
=====Define a node=====
A node must belong to a coordinate, either the global coordinate system or a local coordinate system. Besides the coordinate ID, you still need to specify its No. and x, y, z values.
[[Image:Modal_Manual_36.png|framed|none]]
=====Directions of a node=====
In Modal, it<nowiki>’</nowiki>s very important that the directions of a node are defined in the local coordinate system.
In a local Cartesian coordinate, all the points have the same directions with local axis. These three directions accord with right-hand rule.
[[File:cartesian.png|framed|none]]
In a local cylindrical coordinate: the x direction vector start from the cross point ''O''<nowiki>’</nowiki> to node point ''P''; the z direction is the same as local ''Z''<sub>''L''</sub> axis; and the y direction is tangential to the circle. These three directions accord with right-hand rule.
[[Image:Modal_Manual_05.png|framed|none]]
In a local spherical coordinate: the x direction vector start from the origin point to node point ''P''; the y direction is tangential to the longitude circle; and the z direction is tangential to the latitude circle. These three directions accord with right-hand rule.
[[File:spherical.png|framed|none]]
----
====Links====
Two types of link are supported in Modal: lines and polygons.
A line is defined by two nodes. For instance, "3 5" defines a trace line between node 3 and node 5.
A polygon is defined by a sequence of nodes. You are allowed to define a polygon with arbitrary number of nodes, which should be arranged according to the clockwise or anticlockwise direction. For instance, "1 2 3 4 5 6" defines a hexagon.
===Geometry in Modal software===
To build a geometry model in the Modal software, you have three methods at least:
* Use the integrated function for geometry modeling in Modal
*  Import geometry from UFF files;
* Create geometry information in the Excel, and then copy and paste them to the  "Config" view.
====geometry modeling illustration====
In this section, the process of creating an uneven spaced plate is introduced.
[[Image:Modal_Manual_37.png|framed|none]]
The plate is 10 in width, and 114 in length, which is divided into 12 segments. The first 4 segments (A) and last four segments (C) are evenly distributed with an interval of 8, and the middle 4 segments (B) are evenly distributed with an interval of 12.5. To ensure the nodes numbered continuously, the following steps should be processed:
*  Segment A. The parameters should be set as below:
[[Image:Modal_Manual_38.png|framed|none]]
The structure showed as below is got：
[[Image:Modal_Manual_39.png|framed|none]]
* Segment B. The origin point of segment B should be node 9. The value of Point on X-Axis and Point in XZ-Plane will be changed automatically.
[[Image:Modal_Manual_40.png|framed|none]]
The structure showed as below is got：
[[Image:Modal_Manual_41.png|framed|none]]
* Segment C. The origin point of segment C should be node 19. The value of Point on X-Axis and Point in XZ-Plane will be changed automatically.
[[Image:Modal_Manual_42.png|framed|none]]
[[Image:Modal_Manual_43.png|framed|none]]
*  Note that there are some repeated nodes, for example, node 9 and node 11, node 10 and node 12. Remove all the repeated nodes by pressing the button of "validity check" [[Image:Modal_Manual_44.png]].
[[Image:Modal_Manual_45.png|framed|none]]
* Note that the IDs of nodes are not continuous now. Renumber all the nodes in-order by pressing the button[[Image:Modal_Manual_46.png]]. The task of modeling has been accomplished by now.
[[Image:Modal_Manual_47.png|framed|none]]
====Basic geometry library====
Geometry modeling is realized in the "Config" view or 3D "Geometry" view by operating the relevant toolbar and right click menu. The location, shape, mesh and numbering of a 3D object can be totally specified by setting its local coordinate system, mesh type, first ID and properties. Several internal 3D objects are included in Modal, such as Line Segments, Line, Rectangle, Trapezia, Sector, Elliptic Sector, Cube, Elliptic Cylinder, Cone, and Sphere.
When bundling several 3D objects together, there may exist some repeated nodes, which will lead to some problems. It<nowiki>’</nowiki>s recommended to delete these repeated nodes. You can finish this task conveniently in Modal.
=====Local coordinate systems=====
Each new 3D object will be created with a new local coordinate, whose type depends on the different kinds of object. You should define the origin point and coordinate frame in the below interface.
The local coordinate is determined by three geometry point in Modal.
[[Image:Modal_Manual_48.png|framed|none]]
The ID# will be specified automatically. Of course you can change it if necessary. You can type the three points manually, or select an existed node from the "Node" list. If a node is selected, its global coordinate value will be filled into the blanks automatically.
Note: On the icons for adding 3D objects in the toolbar, the light blue point indicates the origin of local coordinate system. For example, the icon[[Image:Modal_Manual_49.png]] indicates that the origin of a rectangle object lies in its bottom left corner.
Moreover, there is hyperlink text of "Illustration" on the dialog of setting properties. Illustration graph of 3D object to be added will show when moving cursor on it.
=====Mesh type=====
[[Image:Modal_Manual_50.png|framed|none]]
This option allows you to set the mesh type to frame or surface. If the surface type is selected, the meshed can be rendered. For a line object, only the frame type is optional.
=====st ID=====
This option allows you to set the first node ID of a new 3D object. Modal automatically assigns the 1st ID for the new object. It<nowiki>’</nowiki>s recommended to set this parameter equal or large than the default value for a primary user.
Of course, in some occasions, setting the 1st ID flexibly will greatly reduce the workload for an advanced user.
=====Properties=====
* '''Line Segments'''
[[Image:Modal_Manual_51.png|framed|none]]
Add line segments between two specified nodes. If "Only Nodes" is checked, then the links will not be added.
* '''Line'''
[[Image:Modal_Manual_52.png|framed|none]]
Only the length and number of segments are required for a line object. The line is along the X axis of local coordinate, and its local origin locates in the left fringe. The node IDs are increasing from its left to right. The new coordinate is of Cartesian type.
[[Image:Modal_Manual_53.png|framed|none]]
* '''Rectangle'''
[[Image:Modal_Manual_54.png|framed|none]]
Length, width and their number of segments should be specified for a rectangle object. The local origin of a rectangle object locates in its bottom left corner. The node IDs are increasing from its left to right. The nodes are numbered from the origin, in the turn of from left to right and from bottom to top. The new coordinate is of Cartesian type.
[[Image:Modal_Manual_55.png|framed|none]]
* '''Trapezia'''
[[Image:Modal_Manual_56.png|framed|none]]
Upper side length, nether left side length, nether right side length, height and their number of segments should be specified for a trapezia object. The local origin of a trapezia object is the intersection point of left height line and nether side, which is shown as the red point in the figure below. The nodes are numbered in the turn of from bottom to top and from left to right. The new coordinate is of Cartesian type.
[[Image:Modal_Manual_57.png|framed|none]]
If the length of nether left side or nether right side is equal to zero, it<nowiki>’</nowiki>s a right-angle trapezia. If both of them are equal to zero, it<nowiki>’</nowiki>s a rectangle. If the length of upper side is equal to zero, it<nowiki>’</nowiki>s a triangle.
* '''Sector'''
[[Image:Modal_Manual_58.png|framed|none]]
The shape of a sector object is specified by the sector angle, inner radius and outer radius. To mesh the sector you should set the number of segments of sector angle and radius. The local origin of a sector object is right the circle center. The sector object is distributed symmetrically to the Y axis of local coordinate system. The nodes IDs are increasing from inner to outer in the anticlockwise direction. The new coordinate is of Cylindrical type.
[[Image:Modal_Manual_59.png|framed|none]]
If the sector angle is equal to 360 degrees, it<nowiki>’</nowiki>s a hollow cirque. If the inner radius is equal to zero, it<nowiki>’</nowiki>s a solid sector. If the sector angle is equal to 360 degrees, and the inner radius is equal to zero, it<nowiki>’</nowiki>s a solid circle.
* '''Elliptic Sector'''
[[Image:Modal_Manual_60.png|framed|none]]
The shape of an elliptic sector object is specified by the sector angle, long radius and short radius. To mesh the elliptic sector you should set the number of segments of sector angle and radius. The local origin of a elliptic sector object is right the ellipse center. The nodes IDs are increasing from inner to outer in the anticlockwise direction. The new coordinate is of Cartesian type.
[[Image:Modal_Manual_61.png|framed|none]]
If the sector angle is equal to 360 degrees, it<nowiki>’</nowiki>s an ellipse. If the long radius is equal to the short radius, it<nowiki>’</nowiki>s a circle sector, which is the same as the sector object introduced above. If the sector angle is equal to 360 degrees, and the long radius is equal to the short radius, it<nowiki>’</nowiki>s a solid circle too.
* '''Cube'''
[[Image:Modal_Manual_62.png|framed|none]]
Length, width, height and their number of segments should be specified for a cube object. The local origin of a cube object locates in the nether left corner of the front side, which is shown as the red point in the figure below. The nodes are numbered from the origin, and the IDs are increasing from nether to upper in the anticlockwise direction. The new coordinate is of Cartesian type.
[[Image:Modal_Manual_63.png|framed|none]]
There is neither top side nor bottom side in this cuboid object. If necessary, you can bundle this object with two rectangle objects, and then remove the repeated nodes to get a cube with all six sides. If the length, width and height are all equal, it<nowiki>’</nowiki>s a cube.
* '''Elliptic Cylinder'''
[[Image:Modal_Manual_64.png|framed|none]]
Long axis and short axis and height should be specified for an elliptic cylinder object. To mesh this object you should set the number of segments of circumference and height. The local origin of an elliptic cylinder object is right the ellipse center of bottom side. The nodes are numbered from the Y axis of local coordinate, and the IDs are increasing from bottom to top in the anticlockwise direction. If the cross section is an circle, the new coordinate is of Spherical type. If the cross section is an ellipse, the new coordinate is of Cartesian type.
[[Image:Modal_Manual_65.png|framed|none]]
There is neither top side nor bottom side in this elliptic cylinder object. If necessary, you can bundle this object with two sector or elliptic sector objects, and then remove the repeated nodes to get a elliptic cylinder with top and bottom sides.
If the long axis is equal to the short axis, it<nowiki>’</nowiki>s a common cylinder.
* '''Cone'''
[[Image:Modal_Manual_66.png|framed|none]]
Upper radius, nether radius and height should be specified for frustum of a cone object. To mesh this object you should set the number of segments of circumference and height. The local origin of a cone object is right the circle center of bottom side. The nodes are numbered from the Y axis of local coordinate, and the IDs are increasing from bottom to top in the anticlockwise direction. The new coordinate is of Cylinder type.
[[Image:Modal_Manual_67.png|framed|none]]
There is neither top side nor bottom side in this cone object. If necessary, you can bundle this object with two sector or elliptic sector objects, and then remove the repeated nodes to get a cone with top and bottom sides.
If the upper radius or nether radius axis is equal to zero, it<nowiki>’</nowiki>s a complete cone (not a frustum).
* '''Sphere'''
[[Image:Modal_Manual_68.png|framed|none]]
Radius and range of latitude angle should be specified for frustum of a sphere object. The range of a latitude angle is <nowiki>[</nowiki>-90,90<nowiki>]</nowiki> degree. Latitude angle of zero means the equator. Latitude angle of -90 degree means the south pole. Latitude of 90 means the north pole. To mesh this object you should set the number of segments of circumference and latitude angle. The nodes are numbered from the negative Y axis of south latitude plane in the local coordinate, and the IDs are increasing from south to north in the anticlockwise direction. The new coordinate is of Spherical type.
[[Image:Modal_Manual_69.png|framed|none]]
If the latitude angle is greater than -90 degree and less than 90 degree, it<nowiki>’</nowiki>s the frustum of a sphere. There is neither top side nor bottom side in this cone object. If necessary, you can bundle this object with two sector or elliptic sector objects, and then remove the repeated nodes to get a complete frustum of sphere. If the latitude angle ranges from -90 degree to 90 degree, it<nowiki>’</nowiki>s a complete sphere. If the latitude angle ranges from zero to 90 degree, it<nowiki>’</nowiki>s a hemisphere.
====Interactive geometry modelling====
Modal also provides you with functions of interactive geometry modeling. You can add nodes, lines, polygons and 3D objects just by mouse clicking, and realize operations of translation, zoom, rotation, deletion, and so on. The functions are accessible by the Graphics Extra Toolbar.
The graphics extra toolbar is available only when geometry, mode shape or ODS animation are showed in the current main window. It is used to control the 3 dimension graphics and animations. This toolbar is the same as configuration extra toolbar, only different buttons are enabled, and its floating style is as below:
The functions of each button as follows:
[[Image:Modal_Manual_70.png]]: Show the interface for geometry modeling
[[Image:Modal_Manual_71.png]]: Delete the selected items
[[Image:Modal_Manual_72.png]]: Check all items, and remove the repeated nodes
[[Image:Modal_Manual_73.png]]: Renumber all the nodes in-order
[[Image:Modal_Manual_74.png]]: Undo the last action
[[Image:Modal_Manual_75.png]]: Redo the previous undone action
[[Image:Modal_Manual_76.png]]: Reset the layout to show the objects in window
[[Image:Modal_Manual_77.png]]: Show the grid plane or not. There is a dropdown menu below this button:
{|border="2" cellspacing="0" cellpadding="4" width="87%"
|rowspan = "3"|
[[Image:Modal_Manual_78.png|framed|none]]
|<nowiki>:</nowiki> Show the grid plane or not<br>
|-
|<nowiki>:</nowiki> Snap to grid point<br>
|-
|<nowiki>:</nowiki> Call the dialog to set the parameters of grid plane<br>
|}
[[Image:Modal_Manual_79.png|framed|none]]
Referring to the global coordinate or some local coordinate, the position of the grid plane can be set by changing the parameters in the dialog. With the grid plane, you<nowiki>’</nowiki>ll be convenient to edit the geometry, such as adding a node or moving a node. Note that the coordinate values displayed are all relative to the reference coordinate, and in the format of Cartesian, even if the reference coordinate is of cylinder or sphere type.
[[Image:Modal_Manual_80.png]]: Add line segments between two nodes. There is a dropdown menu below this button:
[[Image:Modal_Manual_81.png|framed|none]]
<nowiki>:</nowiki> To select nodes by mouse. There is a dropdown menu below this button:
[[Image:Modal_Manual_82.png|framed|none]]
[[Image:Modal_Manual_83.png]]: Show the default 3D view. There is a dropdown menu below this button:
[[Image:Modal_Manual_84.png|framed|none]]
[[Image:Modal_Manual_85.png]]: Display the transparent surface of un-deformed structure. There is a dropdown menu below this button:
[[Image:Modal_Manual_86.png]]: Render animation surface (for polygon elements) of not
[[Image:Modal_Manual_87.png]]: Show the single view or quad view in the window
[[Image:Modal_Manual_88.png]]: Select mode No. from the list (for mode shape animation)
[[Image:Modal_Manual_89.png]]: Turn to next mode (for mode shape animation)
[[Image:Modal_Manual_90.png]]: Turn to previous mode (for mode shape animation)
====Import geometry====
You can import geometry information from UFF 15/82/2412 files and IGES files.
[[Image:Modal_Manual_91.gif|framed|none]]
You can create geometry information in the Excel, and then copy and paste them to the  "Config" view.
[[Image:Modal_Manual_92.png|framed|none]]
==Data acquisition==
Data acquisition is a critical step for modal analysis: without correct data, no exploitable results. Thanks to the direct acquisition implemented in Modal, enjoy the Teamwork analyzers power and accuracy with a dedicated interface for structural acquisition. The interface works with the different excitation modes: impact hammer, shaker, operating excitation.
[[File:Modal_Manual_03.jpg|framed|none]]
To excite a large structure, up to 6 shakers per analyzers can receive signals from generators outputs. In order to fit the wide range of potential cases, the complete series of excitation signals from random, chirp, swept sine, stepped sine to normal modes can be generated.
[[File:plane.png|framed|none]]
For high channel count applications, Teamwork technology cascades several analyzers together to acquire simultaneously hundreds of channels. Teamwork instruments guarantee an efficient instrumentation thanks to the different possible configuration.
[[Image:Modal_Manual_06.jpg|framed|none]]
For example, this flexibility allows to highly reduce the cable length by distributing the instruments along the structure under test.
The direct data acquisition (DAQ) module is available in Modal, which enables you to complete a modal test easily and quickly.
Launch the DAQ by clicking the "Data Acquisition" item, shown as the following.
[[Image:Modal_Manual_93.png|framed|none]]
Then the geometry modeled in Modal will be transferred to DAQ automatically.
[[Image:Modal_Manual_94.png|framed|none]]
To perform a complete modal acquisition, follow the different steps described here.
===Test planning===
In the preparation panel, set the test planning.
[[Image:Modal_Manual_95.gif|framed|none]]
[[Image:Modal_Manual_96.png|framed|none]]
===Transducers definition===
Set the transducer list in the <nowiki>’</nowiki>Transducers<nowiki>’</nowiki> page of Preparation Pane. Note to select the correct transducer type and fill the correct sensitivity.
[[Image:Modal_Manual_97.png|framed|none]]
Check the different mesurements directly on the geometry
[[Image:Modal_Manual_98.gif|framed|none]]
The references are displayed in red and the roving DOFs in green.
===Measurement parameters setup===
* Parameters Panel-<nowiki>></nowiki>Channel: set range for each active channel; match them to the corresponding measurement DOFs and transducers.
[[Image:Modal_Manual_99.png|framed|none]]
* Parameters Panel-<nowiki>></nowiki>Measurement: set the frequency range, spectral lines, average number, and window type.
[[Image:Modal_Manual_100.png|framed|none]]
* Parameters Panel-<nowiki>></nowiki>Trigger
[[Image:Modal_Manual_101.png|framed|none]]
===Display ans save options===
Action Panel-<nowiki>></nowiki>Display and Save: set the data blocks you want to display and export. As the following graph, trigger block, FRF H1, and coherence will be displayed, trigger block and FRF H1 will be exported in the Binary UFF format. You can go to this data storage directory to check files by pressing button [[Image:Modal_Manual_102.png]].
[[Image:Modal_Manual_103.png|framed|none]]
===Analyzer connection===
Click the button on the toolbar showed as the following to lunch NVGate and connect to it. During this process, you may be asked to operate the wizard of NVGate. You should confirm that the NVGate has been launched successfully before pressing the <nowiki>’</nowiki>OK<nowiki>’</nowiki> button.
[[Image:Modal_Manual_104.png|framed|none]]
If necessary, you may need to set the environment parameters of DAQ by the menu of <nowiki>’</nowiki>Operation<nowiki>’</nowiki>-<nowiki>>’</nowiki>Environment setting<nowiki>’</nowiki>. Please refer to the online help of DAQ for more details
[[Image:Modal_Manual_105.png|framed|none]]
Note that for acquisition with several synchronized analyzers, NVGate V10 minimum is required.
===Acquisition control===
Control Panel-<nowiki>></nowiki>Control: press  [[Image:Modal_Manual_106.png]]to begin the measurement, [[Image:Modal_Manual_107.png]]to pause, and
[[Image:Modal_Manual_108.png]]to stop. If the <nowiki>’</nowiki>Auto Run<nowiki>’</nowiki> option is checked, the measurement sets will be executed automatically one by one, you don<nowiki>’</nowiki>t need to press the button [[Image:Modal_Manual_109.png]]
after one measurement set is finished. <nowiki>’</nowiki>Normal<nowiki>’</nowiki>, <nowiki>’</nowiki>Manual Accept<nowiki>’</nowiki> and <nowiki>’</nowiki>Overload Rejection<nowiki>’</nowiki> are different modes to accept the triggered data. You can also set <nowiki>’</nowiki>Double Hit Rejection<nowiki>’</nowiki> to reject the continuous hits when performing a hammer impact test to get better measurement quality.
[[Image:Modal_Manual_110.png|framed|none]]
When the acquisition is completed, press the button of [[Image:Modal_Manual_111.png]] or [[Image:Modal_Manual_112.png]] to transfer the data to the Modal main interface and start the modal identification.
==Signal processing==
Signal processing wizard is designed to set the parameters for signal processing. Many signal estimations can be realized, such as power spectrum estimation, multiple input multiple output frequency response function estimation, and coherence function estimation, and so on. Five steps should be performed in this wizard: Estimation,  Detrending, Decimation, Fast Fourier Transform (FFT)], and  Windowing.
===Estimation===
[[Image:Modal_Manual_113.png|framed|none]]
Various signal estimation process can be set in this page. You must estimate the <nowiki>’</nowiki>FRF<nowiki>’</nowiki> if you want to perform modal parameters identification in the case of EMA. H1,H2 and Hc are three different methods for FRF estimation. Reference signal is needed for Hc method. You must estimate the <nowiki>’</nowiki>Output PSD Matrix<nowiki>’</nowiki>(for OMA NarBand Full) or <nowiki>’</nowiki>Output half PSD<nowiki>’</nowiki>(for OMA BroBand, OMA NarBand Half, and so on) if you want to perform modal parameters identification in the case of OMA.
The next step of signal processing wizard is  Detrending.
===Detrending===
[[Image:Modal_Manual_114.png|framed|none]]
The purpose of detrending is to condition the time domain signals, remove their constant or linear trend.
The previous step of signal processing wizard is  Estimation, and the next step is  Decimation.
===Decimation===
[[Image:Modal_Manual_115.png|framed|none]]
The purpose of decimation is to reduce the range of analysis frequency. For example, you are interest in the frequency range of 0<nowiki>~</nowiki>10 Hz, and the sampling frequency is 256 Hz, then you should set the decimation points to 10.
The basic principle of decimation is reserve part of points and removing the others: if the decimation points is N, the length of data will be 1/N of original data. To prevent the estimation from frequency aliasing, a low-pass filter is necessary in this process.
There are not any anti-aliasing filters in some low-cost data acquisition. It will greatly improve the quality of estimation for you to sample data with high frequency and then decimate them in Modal, partly compensating for the loss of anti-aliasing filters.
The previous step of signal processing wizard is Detrending, and the next step is setup of FFT].
===Setup of FTT===
[[Image:Modal_Manual_116.png|framed|none]]
In this page, parameters for fast Fourier transform (FFT) will be set to transfer the time domain signals to frequency domain.
<nowiki>’</nowiki>Sequential Sampling<nowiki>’</nowiki> means that the data was sampled sequentially, without any pause. A typical instance is to sample data sequentially under random excitation. "Periodic Sampling<nowiki>’</nowiki> means that the data in the file was sampled periodically. A typical instance is to sample multiple frames of data in a hammer impact test, for the sake of performing average in the spectrum estimation. The practical significance of "Periodic Sampling" is the overlap percent is set to zero in FFT.
<nowiki>’</nowiki>FFT Points<nowiki>’</nowiki> specifies the length of each segment in the transform. The optional list will be confirmed by the software according to the length of imported data automatically. You can select one from this list. When the data points has less than <nowiki>’</nowiki>FFT points<nowiki>’</nowiki>, zeros will be padded, and truncated if it has more.
<nowiki>’</nowiki>Overlapping<nowiki>’</nowiki> specifies the percent of overlap between each segment. The purpose of overlap is to increase the times of average. For an example of 2048 data length and 1024 FFT points, if the overlap percent is set to 0, the original data can be divided into two segments for FFT (the first segment is from 1 to 1024, and the second part is from 1025 to 2048); When the overlap percent is set to 50%, the number of overlap points is 512, and the original data can be divided into three segments (the first segment is from 1 to 1024, and the second segment is from 513 to 1536, and the third segment is from 1025 to 2048).
<nowiki>’</nowiki>Average No.<nowiki>’</nowiki> specifies the number of average during the FFT calculation. Its default value is 0, which means the maximum possible average numbers. When the number specified by the user is larger than the maximum average number, it will be modified to the maximum average number automatically
The previous step of signal processing wizard is decimation, and the next step is windowing.
===Windowing===
[[Image:Modal_Manual_117.png|framed|none]]
You can specify the windowing functions for the FFT in this page. The truncation and non-periodicity of signal will cause energy leakage and lead to alias error in the frequency domain. The main purpose of windowing is adding time weight functions to the signal to filter the non-periodicity part and reduce leakage. Six kind of window function such as <font color="#0000FF"><u>Boxcar</u></font>, <font color="#0000FF"><u>Exponential</u></font>, <font color="#0000FF"><u>Force & Exponential</u></font>, <font color="#0000FF"><u>Hanning</u></font>, <font color="#0000FF"><u>Hamming</u></font>, <font color="#0000FF"><u>Flattop</u> </font>is provided and can be employed for different cases.
====Boxcar====
Boxcar window, called as Transient window also, has the shape of rectangle. It adds the same weight to all parts of the time history, i.e. no weight is added.
The Boxcar function has a value of 1 over its length and it only truncation the signal simply. It can be applied to the signal such as periodic (period random) and transient (Chirp, Burst Chirp) signal generally.
====Exponential====
The shape of the exponential window is that of a decaying exponential. By assigning the time const, the exponential window damps the signal, ensuring that the signal fully decays by the end of the sample block.
Exponential function can be applied commonly to the measurement of light damping system.
The following equation defines the exponential window:
W(t)=e<sup>-βt</sup>
Where β is a constant. In Modal, Td is defined as the exponential decay time over which exponential window function decays from 1 to 1/e, in this case , β=1/ Td. When applying exponential function to a signal, damping of the system will be increased and should be modified. The damping ratios and frequencies can be automatically modified in Modal if the exponential window is applied by the signal processing wizard. When the input data is FRFs which were estimated by applying exponential window, you should remember to specify the decay time (with unit of ms) in the configuration file.
'''Note: '''The value you should fill in this interface is not β, but the percentage of β constitutes to the sampling period.
====Force & Exponential====
In a force window, the front part of the signal is preserved and the others are set to 0. The time length of the preserved signal is named force width. When Force & Exponential window is selected, exponential window is applied to both channels while force window is only applied to the reference channel.
Force window is very useful for the hammer impact test and it can wipe off the fluctuation of the force signal and greatly improve SNR (Signal Noise Ratio).
'''Note:''' You should fill the percentage of these values constitute to the sampling period as well.
====Hanning====
Hanning window is also named random window and has a shape similar to that of half a cycle of a cosine wave. It decays the start and end part of the signal and enforce the signal to become periodic.
It is a general-purpose window and its typically applied to the test excited by random noise.
====Hamming====
Hamming window is similar to Hanning window and it can further decrease the side lobe.
====Flattop====
Namely cosine window, the flattop has the flatness power shape and the higher amplitude accuracy while poor frequency resolution.
The flattop window is most useful in accurately measuring the amplitude of specified frequency components such as filter characters.
This is the last step of the signal processing wizard, and the previous step is setup of FFT. Press the <nowiki>’</nowiki>Finish<nowiki>’</nowiki> button to confirm all the parameters set in the wizard, and you can begin to signal processing now.
The sampling times can be set to 2.56 or 2. Usually in an EMA analysis it is set to 2.56, and in an OMA analysis it is set to 2. If the sampling times is 2.56, then the number of the spectral line will be 1/2.56 of the FFT length, and the analysis frequency range will be 1/2.56 of the sampling frequency. If the sampling times is 2, then the number of the spectral line will be half of the FFT length, and the analysis frequency range will be half of the sampling frequency.
After signal processing, the result data will be displayed under the directory of <nowiki>’</nowiki>Data\Setup?\Estimate" in the <nowiki>’</nowiki>Data<nowiki>’</nowiki> page of workspace short pane, such as FRF (frequency response function), COH (coherence function), Pxx (input auto power spectral density function), Pyy (output auto power spectral density function), Pxy (input and output cross power spectral density function), OPSD (output power spectral density matrix) and HPSD (half power spectral density function). Double click these items, and relevant curves or lists will be displayed in the main window.
If you want to do signal processing with other parameters, please run the wizard and process again. Before the new signal processing, all the result got from last signal processing will be refreshed or deleted automatically.


==ODS & Modal Analysis==
==ODS & Modal Analysis==
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