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1.3  Understanding the Toolbox architecture

• Layers of code
• Infos in Stack
• Global variables

1.3.1  Layers of code

The SDT has three layers of code.

• Graphical user interfaces (feplot, iiplot, ii_mac) provide a layer of predefined operations for Frequency Response Function (FRF) visualization and analysis, identification, 3-D deformation animation, and test/analysis correlation. Graphically supported operations (interactions between the user and plots/ menus/mouse movements/key pressed) form a subset of commands provided by user interface functions.

  The policy of the GUI layer is to let the user free to perform his own operations at any point. Significant efforts are made to ensure that this does not conflict with the continued use of GUI functions. But it is accepted that it may exceptionally do so, since command line and script access is a key to the flexibility of SDT. In most such cases, clearing the figure (using clf) or in the worst case closing it (use close or delete) and replotting will solve the problem.

• User interface (UI) functions provide high level solutions to problems in identification, finite element mesh handling, model reduction, sensor placement, superelement handling or parameterized models for FE model update. The first argument to these functions is a string command which is parsed to know what operations to perform. See commode for conventions linked to parsed commands.
• Scientific functions implement standard and state of the art methods in experimental modal analysis, Finite Element analysis, and to some extent in structural design and FE model update. These functions are open and can be easily extended to suit particular needs using the scientific environment provided by MATLAB.

1.3.2  Infos in Stack

When extensible and possibly large lists of mixed data are needed, SDT uses .Stack fields which are N by 3 cell arrays with each row of the form {'type','name',val}. The purpose of these cell arrays is to deal with unordered sets of data entries which can be classified by type and name.

stack_get, stack_set and stack_rm commands are low level commands used to get/set/remove single or multiple entries from stacks. Higher level pointer access to stacks stored in iiplot (curve stacks) and feplot (model and case stacks) are described in section 2.1.2 and section 4.2.3.

1.3.3  Global variables

Pointers to variables stored in graphical objects are now prefered to global variables. The user interface for data visualization and identification (iicom, idcom, iiplot) no longer uses global variables, see section 2.1.6 for compatibility information. femesh and upcom are the only functions that use global variables.

User interfaces require knowledge of the current state of the interface and appropriate data. The policy of the Toolbox is to let the user free to perform his own operations at any point. Significant efforts are made to ensure that this does not conflict with the continued use of GUI functions, but it is accepted that it may exceptionally do so. This flexibility resulted in the use of both global variables (for information that the user is likely to modify) and graphical objects (for other information).

The femesh user interface for finite element mesh handling uses a number of standard global variables shown below

By default, femesh automatically use base workspace definitions of the standard global variables: base workspace variables with the correct name are transformed to global variables even if you did not dot it initially. When using the standard global variables within functions, you should always declare them as global at the beginning of your function. If you don't declare them as global modifications that you perform will not be taken into account, unless you call femesh, ... from your function which will declare the variables as global there too. The only thing that you should avoid is to use clear and not clear global within a function and then reinitialize the variable to something non-zero. In such cases the global variable is used and a warning is passed.