symReadSSCVariables

Load variables from Simscape component

Syntax

[names,values,units] = symReadSSCVariables(componentName)
[names,values,units] = symReadSSCVariables(componentName,'ReturnFunctions',true)

Description

example

[names,values,units] = symReadSSCVariables(componentName) returns cell arrays containing the names, values, and units of all variables from the Simscape™ component called componentName.

example

[names,values,units] = symReadSSCVariables(componentName,'ReturnFunctions',true) returns the names as symbolic functions of variable t.

Examples

collapse all

Load the names, values, and units of the variables of a Simscape component.

Suppose you have the Simscape component friction.ssc in your current folder.

type('friction.ssc');
component friction < foundation.mechanical.rotational.branch

parameters
    brkwy_trq = { 25, 'N*m' };          % Breakaway friction torque
    Col_trq = { 20, 'N*m' };            % Coulomb friction torque
    visc_coef = { 0.001, 'N*m*s/rad' }; % Viscous friction coefficient
    trans_coef = { 10, 's/rad' };       % Transition approximation coefficient
    vel_thr = { 1e-4, 'rad/s' };        % Linear region velocity threshold
end

parameters (Access=private)
    brkwy_trq_th = { 24.995, 'N*m' };   % Breakaway torque at threshold velocity
end

function setup
    % Parameter range checking
    if brkwy_trq <= 0
        pm_error('simscape:GreaterThanZero','Breakaway friction torque' )
    end
    if Col_trq <= 0
        pm_error('simscape:GreaterThanZero','Coulomb friction torque' )
    end
    if Col_trq > brkwy_trq
        pm_error('simscape:LessThanOrEqual','Coulomb friction torque',...
                 'Breakaway friction torque')
    end
    if visc_coef < 0
        pm_error('simscape:GreaterThanOrEqualToZero','Viscous friction coefficient')
    end
    if trans_coef <= 0
        pm_error('simscape:GreaterThanZero','Transition approximation coefficient')
    end
    if vel_thr <= 0
        pm_error('simscape:GreaterThanZero','Linear region velocity threshold')
    end

    % Computing breakaway torque at threshold velocity
    brkwy_trq_th = visc_coef * vel_thr + Col_trq + (brkwy_trq - Col_trq) * ...
        exp(-trans_coef * vel_thr);
end

equations
    if (abs(w) <= vel_thr)
        % Linear region
        t == brkwy_trq_th * w / vel_thr;
    elseif w > 0
        t == visc_coef * w + Col_trq + ...
            (brkwy_trq - Col_trq) * exp(-trans_coef * w);
    else
        t == visc_coef * w - Col_trq - ...
            (brkwy_trq - Col_trq) * exp(-trans_coef * abs(w));
    end
end

end

Load the names, values, and units of the variables of the component friction.ssc.

[names,values,units] = symReadSSCVariables('friction.ssc');

In this example, all elements of the resulting cell arrays are scalars. You can convert the cell arrays to symbolic vectors.

names_sym = cell2sym(names)
names_sym =
[ t, w]
values_sym = cell2sym(values)
values_sym =
[ 0, 0]

Create individual symbolic variables from the elements of the cell array names in the MATLAB® workspace. This command creates the symbolic variables t and w as sym objects in the workspace.

syms(names)

Load the names of the variables of a Simscape component while converting them to symbolic functions of the variable t.

Suppose you have the Simscape component source.ssc in your current folder.

type('source.ssc');
component source
% Electrical Source
% Defines an electrical source with positive and negative external nodes.
% Also defines associated through and across variables.

nodes
    p = foundation.electrical.electrical; % :top
    n = foundation.electrical.electrical; % :bottom
end

variables(Access=protected)
    i = { 0, 'A' }; % Current
    v = { 0, 'V' }; % Voltage
end

branches
    i : p.i -> n.i;
end

equations
     v == p.v - n.v;
end

end

Load the names of the variables of the component source.ssc by setting 'ReturnFunctions' to true.

[names,~,~] = symReadSSCVariables('source.ssc','ReturnFunctions',true);

In this example, all elements of the resulting cell arrays are scalars. You can convert the cell arrays to symbolic vectors.

names_symfun = cell2sym(names)
names_symfun =
[ i(t), v(t)]

Create individual symbolic functions from the elements of the cell array names in the MATLAB workspace. This command creates the symbolic functions i and v as symfun objects, and their variable t as a sym object in the workspace.

syms(names)

Input Arguments

collapse all

Simscape component name, specified as a file name enclosed in single quotes. The file must have the extension .ssc. If you do not provide the file extension, symReadSSCVariables assumes it to be .ssc. The component must be on the MATLAB path or in the current folder.

Example: 'MyComponent.ssc'

Output Arguments

collapse all

Names of all variables of a Simscape component, returned as a cell array.

Data Types: cell

Values of all variables of a Simscape component, returned as a cell array.

Data Types: cell

Units of all variables of a Simscape component, returned as a cell array.

Data Types: cell

Introduced in R2016a