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2.1  iiplot interface tutorial

• The main figure
• Toolbar
• Mouse operation and keyboard shortcuts
• Context menus
• The curve stack
• Handling what you display, axes and channel tabs
• Importing FRF data
• SDT 5 compatibility
• iiplot for signal processing

iiplot is the response viewer used by SDT. It is essential for the identification procedures but can also be used to visualize FEM simulation results.

As detailed in section 2.3, identification problems should be solved using the standard commands for identification provided in idcom while running the iiplot interface for data visualization. To perform an identification correctly, you need to have some familiarity with the interface and in particular with the iicom commands that let you modify what you display.

2.1.1  The main figure

For simple data viewing you can open an iiplot figure using ci=iiplot (or ci=iiplot(2) to specify a figure number). For identification routines you should use ci=idcom (standard datasets are then used see section 2.3).

To familiarize yourself with the iiplot interface, run demosdt('demogartidpro'). Which opens the iiplot figure and the associated iiplot(2) properties figure whose tabs are detailed in the following sections.

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Figure 2.1: Display figure of the iiplot interface.

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Toolbar

	Toggles the display or not of the iiplot property figure
	Previous channel/deformation, see iicom ch+
	Next channel/deformation
	Fixed zoom on FRF, see iicom wmin. Note that the variable zoom (drag box) is always active, see iimouse zoom
	Start cursor, see iimouse Cursor
	refresh the displayed axes

Mouse operation and keyboard shortcuts

Mouse and keypress operations are handled by iimouse within iiplot, feplot, and ii_mac figures. For a list of active keys press ? in the current figure.

Drag your mouse on the plot to select a region of interest and see how you directly zoom to this region. Double click on the same plot to go back to the initial zoom. On some platforms the double click is sensitive to speed and you may beed to type the i key with the axis of interest active. An axis becomes active when you click on it.

Open the ContextMenu associated with any axis (click anywhere in the axis using the right mouse button), select Cursor, and see how you have a vertical cursor giving information about data in the axis. To stop the cursor use a right click or press the c key. Note how the left click gives you detailed information on the current point or the left click history. In iiplot you can for example use that to measure distances.

Click on pole lines (vertical dotted lines) and FRFs and see how additional information on what you just clicked on is given. You can hide the info area by clicking on it.

Context menus

The axes ContextMenu (click on the axis using the right mouse button) lets you select , set axes title options, set pole line defaults, ...

• Cursor tracks mouse movements and displays information about pointed object. For ODS cursor see iicom ods.
• Show chooses what to display.
• Compute... [MMIF,CMIF...] chooses what to compute and display. The iicom('show [MMIF,CMIF...]') command line is similar. Details on what can be computed are given in ii_mmif.
• Variables in current axis... chooses which variable to display, see iicom IIx.
• iiplot properties, same as iicom('pro'), opens the property figure
• Scale...[x lin, x log...] chooses the axis scale as the. See iicom xlin or use iimouse('axisscale[xlin,xlog...]') commands.
• TitOpt chooses the title, axis and legend labels-format.
• PoleLine pole line selection.
• Views... chooses the views, see iimouse view.
• colorbar shows the colorbar and is equivalent to cingui('ColorBarMenu') command line.
• Zoom reset is the same as the iimouse('resetvie') command line to reset the zoom.
• setlines calls the associated function

The line ContextMenu lets you can set line type, width, color ...

The title/label ContextMenu lets you move, delete, edit ... the text

After running through these steps, you should master the basics of the iiplot interface. To learn more, you should take time to see which commands are available by reading the Reference sections for iicom (general list of commands for plot manipulations), iimouse (mouse and key press support for SDT and non SDT figures), iiplot (standard plots derived from FRFs and test results that are supported).

2.1.2  The curve stack

iiplot considers data sets in the following format

• Response data related to UFF58 format
• Curves generated by SDT
• Shapes at DOFs related to UFF55 format

This data is stored in iiplot figures as a Stack field (a cell array with the first column giving 'curve' type entries, the second giving a name for each dataset and the last containing the data, see stack_get). To allow easier access to the data, SDT handle objects are used. Thus the following calls are equivalent ways to get access to the data

 ci=iicom('curveload','gartid');
 iicom(ci,'pro');iicom(ci,'CurTab Stack'); % show stack tab

 % Normal use: the XF stack pointer
 XF1=iicom(ci,'curvexf');
 XF1(1)             % still the same dataset, indexed by number
 XF1('Test')        % still the same dataset, indexed by name
 XF2=XF1.GetData;   % Copy the data from the figure to variable XF2

 % Alternative refer the figure pointer stack
 ci.Stack{'Test'}  % a copy of the same data, selected by name
 ci.Stack{1,3}     % the same by index
 % Use regular expresion ('II.*' here) for multiple match
 ci=stack_rm(ci,'curve','#II.*')
 % If you really insist on low level calls
 r1=get(2,'userdata'); % object containing the data (same as ci above)
 s=ci.vfields.Stack.GetData % get a copy of the stack (cell array with 
            % type,name,data where data is stored)
 s{1,3}     % the first data set

The ci.Stack handler allows regular expression based access, as for cf.Stack. The text then begins by the # character.

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Figure 2.2: Stack tab of the iiplot interface.

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The graphical representation of the stack shown in figure 2.2 lets you do a number of manipulations witch are available trough the context menu of the list of datasets in the stack

• Compute gives access to data processing commands in ii_mmif. You perform the analysis from the command line with iicom(ci,'sum','Test'). The list of available post processing functions is given by ii_mmif list.
• Load lets you load more data with iicom(ci,'curveload-append','gartid'), replace the current data with iicom(ci,'curveload','gartid')
• Display lets you display one or more selected dataset in the iiplot figure (see corresponding command iicom IIx).
• Save lets you save one or more dataset (see corresponding command iicom CurveSave).
• Join combines selected datasets that have comparable dimensions (see corresponding command iicom CurveJoin).
• Cat concatenates selected datasets along time or frequency dimension (see corresponding command iicom CurveCat).
• Remove removes selected dataset (see corresponding command iicom CurveRemove).
• NewId opens a new idcom figure with the selected dataset (see corresponding command iicom CurveNewId).

2.1.3  Handling what you display, axes and channel tabs

iiplot lets you display multiple axes see iicom Sub. Information about each axis is show in the axes tab.

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Figure 2.3: Axes tabs of the iiplot interface.

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For example open the interface with the commands below and see a few thing you can do

 [ci,XF]=idcom;iicom(ci,'curveload sdt_id');
 XF('IdFrf')=XF('Test'); % copy dataset
 XF('IdFrf').xf=XF('Test').xf*2; % double amplitude
 iicom('curtab Axes');

• Sub Subplots : Type iicom submagpha to display a standard magnitude/phase plot. Open the IIplot:sub commands menu and see that you could have achieved the same thing using this pull-down menu. Note that using ci=iiplot(2); iicom(ci,'SubMagPha') gives you control on which figure the command applies to.
• Show Type iicom(';cax1;showmmi'); to display the MMIF in the lower plot. Go back to the phase, by making axis 1 active (click on it) and selecting phase(w) in the axis type menu (which is located just on the right of the current axis button).
• IIx select sets you want to display using iicom(';showabs;ch1');iicom('iix only',{'Test','IdFrf'}). You could also achieve the same thing using the IIplot:Variables menu.
• Note that when you print the figure, you may want to use the comgui imwrite FileName.ext command or -noui switch so that the GUI is not printed. Example print -noui -depsc2 FileName.eps.
• continue the d_iiplot demo which shows a few other things.

Once you have selected the datasets to be displayed, you can use the channel tab to scan trough the data.

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Figure 2.4: Channel tabs of the iiplot interface.

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Major commands you might want to know

• use the to scan trough different transfer functions. Note that you can also use the + or - keys when a drawing axis is active.
• Go the Channel tab of the property figure and select more than one channel in the list. Note that you can also select channels from the command line using iicom('ch 1 5').

2.1.4  Importing FRF data

There are two main mechanisms to import FRF data into SDT. Universal files are easiest if generated by your acquisition system. Writing of an import script defining fields used by SDT is also fairly simple and described below (you can then use ufwrite to generate universal files for export).

The ufread and ufwrite functions allow conversions between the xf format and files in the Universal File Format which is supported by most measurement systems. A typical call would be

 UFS=ufread('FileName.unv');  % read
 ci=iiplot;                   % initialize iiplot
 ci.Stack{1,3}=UFS(3)         % show UFS(3) in iiplot

where you read the database wrapper UFS (see xfopt), initialize the standard database wrapper XF used by iiplot and idcom, assign dataset 3 of UFS to dataset 1 of XF (assuming that dataset three represents frequency response functions of interest).

Note that some acquisition systems write many universal files for a set of measurements (one file per channel). This is supported by ufread with a stared file name

 UFS=ufread('FileRoot*.unv'); 

Measured frequency responses are stored in the .xf field (frequencies in .w) and should comply with the specifications of the xf format (see details under xf ). Other fields needed to specify the physical meaning of each FRF are detailed in the xfopt reference section. When importing data from your own format or using a universal file where some fields are not correct, the SDT will generally function with default values set by the xfopt function, but you should still complete/correct these variables as detailed below.

For correct display in feplot and title/legend generation, you should set the XF(1).dof field (see section 2.2 for details on geometry declaration, and dof reference). For example one can consider a MIMO test with 2 inputs and 4 outputs stored as columns of variable xf with the rows corresponding to frequencies stored in w. You script will look like

 [ci,XF]=idcom;
 [XF1,cf]=demosdt('demo2bay xf');% sample data and feplot pointer
 out_dof=[3:6]+.02'; % output dofs for 4 sensors in y direction
 in_dof=[6.03 3.01]; % input dofs for two shakers at nodes 1 and 10
 out_dof=out_dof(:)*ones(1,length(in_dof));
 in_dof=ones(length(out_dof),1)*in_dof(:)';
 XF1=struct('w',XF1.w, ...   % frequencies in Hz
            'xf',XF1.xf, ... % responses (size Nw x (40))
            'dof',[out_dof(:) in_dof(:)]);
 XF('Test')=XF1; % sets data and verifies
 ci.IDopt.nsna=size(out_dof,1); % define IDCOM prop
 ci.IDopt.recip='mimo'; % define IDCOM prop
 iicom(ci,'sub');

 cf.def=XF('Test');fecom('ch35'); % frequency of first mode

You can also edit these values using the iiplot properties:channel tab.

For correct identification using id_rc, you should verify the fields of XF(1).idopt. These correspond to the IDcomGUI:Options tab (see section 2.3). You can also edit these values in a script. For correct identification, you should set

 XF=demosdt('demogartid');
 XF(1).idopt.Residual='3';
 XF(1).idopt.DataType='Acc';
 XF(1).idopt.Absci='Hz';XF(1).idopt.PoleU='Hz';
 iicom('wmin 6 40') % sets XF(1).idopt.Selected
 XF(1).idopt.Fit='Complex';
 XF(1).idopt  % display current options

For correct transformations using id_rm, you should also verify IDopt.NSNA (number of sensors/actuators), IDopt.Reciprocity and IDopt.Collocated.

For correct labels using iiplot you should set the abscissa, and ordinate numerator/denominator types in the data base wrapper. You can edit these values using the iiplot properties:channel tab. A typical script would declare frequencies, acceleration, and force using (see list with xfopt _datatype)

 UFS(2).x='Freq';UFS(2).yn='Acc';UFS(2).yd='Load';UFS(2).info

2.1.5  SDT 5 compatibility

With SDT 6, global variables are no longer used and iiplot supports display of curves in other settings than identification.

If you have saved SDT 5 datasets into a .mat file, iicom('CurveLoad FileName') will place the data into an SDT 6 stack properly. Otherwise for an operation similar to that of SDT 5, where you use XF(1).xf rather than the new XF('Test').xf, you should start iiplot in its identification mode and obtain a pointer XF (SDT handle object) to the data sets (now stored in the figure itself) as follows

 >> ci=iicom('curveid');XF=iicom(ci,'curveXF')

XF (curve stack in figure 2) = 

XF(1) : [.w    0x0, xf    0x0] 'Test'  : response (general or unknown) 
XF(2) : [.w    0x0, xf    0x0] 'IdFrf'  : response (general or unknown)
XF(3) : [.w    0x0, xf    0x0] 'IIxh'  : response (general or unknown) 
XF(4) : [.w    0x0, xf    0x0] 'IIxi'  : response (general or unknown) 
XF(5) : [.po   0x0, res   0x0] 'IdMain'  : shape data                  
XF(6) : [.po   0x0, res   0x0] 'IdAlt'  : shape data                   

The following table lists the global variables that were used in SDT 5 and the new procedure to access those fields which should be defined directly.

2.1.6  iiplot for signal processing

iiplot figure lets you perform standard signal processing operations (FFT, MMIF, filtering...) directly from the GUI. Opening iiplot properties figure, they are accessible trough the contextual menu compute (right click on the curve list in the Stack tab). Once an operation has been performed, its parameters can be edited in the GUI, and it can be recomputed using the Recompute button.

Following example deals about a linear spring mass system, with a 20 Hz cosine load applied on the mass.

% Define 1e3 N/m spring and 1 kg mass :
mdl=[]; mdl.Node=[1 0 0 0 0 0 0;2 0 0 0 0 0 1];
mdl.Elt=[Inf abs('celas') 0 0 0; 1 2 -3 3 1 1 1e3 0 3;...
         Inf abs('mass1') 0 0 0; 2 0 0 1 0 0 0 2 0];
% Boundary condition :
mdl=fe_case(mdl,'FixDof','clamped base','z==0'); 
% Load :
mdl=fe_case(mdl,'DofLoad','load 1',2.03); % define load
mdl=fe_curve(mdl,'set','sine','Test cos .05 1');% time evolution of load
mdl=fe_case(mdl,'setcurve','load 1','sine');
 
cf=feplot(mdl);
 
% Time computation :
cf.Stack{'info','TimeOpt'}=....
    struct('Method','Newmark','Opt',[.25 .5 3e-4 1e-3 1e4]); % options
cf.def=fe_time(cf.mdl);
 
ci=iiplot;
fecom(cf,'CursorOnIiplot') % display deformations in iiplot

% all following operations can be performed directly in the GUI:
% see the list of curves contained in iiplot figure, Stack tab:
iicom(ci,'pro');iicom(ci,'curtab Stack');
  % compute FFT of deformations:
ii_mmif('FFT',ci,'deffromfeplot') % compute
iicom(ci,'curtab Stack','fft(deffromfeplot)'); % show FFT options that are editable 
  % edit options & Recompute:
ci.Stack{'fft(deffromfeplot)'}.Set={'fmax',50};
iicom(ci,'curtab Stack','fft(deffromfeplot)','Recompute'); 
 
% filter and display
ii_mmif('BandPass',ci,'deffromfeplot') % compute
ci.Stack{'bandpass(deffromfeplot)'}.Set={'fmin',15,'fmax',25};
iicom(ci,'curtab Stack','bandpass(deffromfeplot)','Recompute'); 
iicom(ci,'iix',{'deffromfeplot','bandpass(deffromfeplot)'});