Set Properties for Analysis

This example shows how to enable analysis by adding stereotypes to model elements and setting property values. The model provides the basis to analyze the trade-off between total cost and weight of the components in a simple architecture model of a robot system. For more information, see Simple Roll-Up Analysis Using Robot System with Properties.

Create a Model Instance for Analysis

Create an instance of the architecture model that you can use for analysis.

An instance is an occurrence of an architecture model element at a given point in time.

An instance freezes the active variant or model reference of the component in the instance model.

An instance model is a collection of instances.

You can update an instance model with changes to a model, but the instance model will not update with changes in active variants or model references. You can use an instance model, saved in a MAT file, of a System Composer architecture model for analysis.

Navigate to Modeling > Analysis Model to open the Instantiate Architecture Model tool. Specify all the parameters required to create and view an analysis model.

The Select Stereotypes tree lists the stereotypes of all profiles that have been loaded in the current session and allows you to select those whose properties should be available in the instance model. You can browse for an analysis function, create a new analysis function, or skip analysis at this point. If the analysis function requires inputs other than elements in the model, such as an exchange rate to compute cost, enter it in Function arguments. Select a mode for iterating through model elements, for example, Bottom-up to move from the leaves of the tree to the root. Strict Mode ensures elements in the instantiated model get properties only if the corresponding element in the composition model has the stereotype applied.

Click Instantiate to create the instantiated architecture model and launch the Analysis Viewer tool.

The Analysis Viewer shows all elements in the first column. The other columns show properties for all stereotypes chosen for the current instance. If a property is not part of a stereotype applied to an element, that field is greyed out. You can use the Filter button to hide properties for certain stereotypes. When you select an element, Instance Properties shows the stereotypes and property values of the element. You can save an instance in a MAT-file and open it again in the Analysis Viewer.

If you make changes in the model while an instance is open, you can synchronize the instance with the model. Update pushes the changes from the instance to the model. Refresh pulls changes to the instance from the model. Unsynchronized changes are shown in a different color. Selecting a single element enables the option to Update Element.

Write Analysis Function

Write a function to analyze the architecture model using instances. An analysis function quantitatively evaluates an architecture for certain characteristics.

An analysis function is a MATLAB^® function that computes values necessary to evaluate the architecture using the properties of each element in the model instance.

Use an analysis function to calculate the result of an analysis.

For more information, see Analysis Function Constructs.

You can add an analysis function as you set up the analysis instance model. After you select the stereotypes of interest, create a template function by clicking next to the Analysis function field. The generated M-file includes the code to obtain all property values from all stereotypes that are subject to analysis. The analysis function operates on a single element — aggregate values are generated by iterating this function over all elements in the model when you run the analysis using the Analysis Viewer tool.

function CostAndWeightRollupAnalysis(instance,varargin)
% Analysis function for the RobotPhysicalArchitecture.slx example

% Calculate total price
if instance.isComponent() && ~isempty(instance.Components)...
 && instance.hasValue('SystemProfile.PhysicalElement.UnitCost')
    sysComponent_unitPrice = 0;
    for child = instance.Components
        if child.hasValue('SystemProfile.PhysicalElement.UnitCost')
           comp_price = child.getValue('SystemProfile.PhysicalElement.UnitCost');
           sysComponent_unitPrice = sysComponent_unitPrice + comp_price;
        end
    end
    instance.setValue('SystemProfile.PhysicalElement.UnitCost',sysComponent_unitPrice);
end

In the generated file, instance is the instance of the element on which the analysis function runs currently. You can perform these operations for analysis:

The getValue function generates an error if the property does not exist. You can use hasValue to query whether elements in the model have the properties before getting the value.

As an example, this code computes the weight of a component as a sum of the weights of its subcomponents.

% Calculate total weight
if instance.isComponent() && ~isempty(instance.Components)...
 && instance.hasValue('SystemProfile.PhysicalElement.UnitWeight')
    weight = 0;
    for child = instance.Components
        if child.hasValue('SystemProfile.PhysicalElement.UnitWeight')
           subcomp_weight = child.getValue('SystemProfile.PhysicalElement.UnitWeight');
           weight = weight + subcomp_weight;
        end
    end
    instance.setValue('SystemProfile.PhysicalElement.UnitWeight',weight);
end

Once the analysis function is complete, add it to the analysis under the Analysis function box. An analysis function can take additional input arguments, for example, a conversion constant if the weights are in different units in different stereotypes. When this code runs for all components recursively, starting from the deepest components in the hierarchy to the top level, the overall weight of the system is assigned to the weight property of the top-level component.

Run Analysis Function

Run an analysis function using the Analysis Viewer.

System Composer runs the analysis function over each model element and computes results. The computed properties are highlighted yellow in the Analysis Viewer.

Here, the total cost of the system is 5100 dollars and the total weight is 55 kg.