Error compiling Simscape network for model: Number of variables exceeds number of equations.

I have modified copy of spring.ssc file from Simscape foundation->translational library, and tried to model simple system but I am getting the error."Number of variables exceeds number of equations", How to identify consistency of equations with variables from available model, and used .ssc files? Some insights I want. Even if you share link containing the information, it will be helpful.

Thanks in advance!

component nspring
% Non-linear Spring
% Behavior is force proportional to square of deformation 

nodes
    r = foundation.mechanical.translational.translational; % r:right
    c = foundation.mechanical.translational.translational; % c:left
end

parameters 
    k = { 1, 'N/(m*m)' };              % Spring constant
end

variables
    v = { 0, 'm/s' };                % Velocity
    f = { 0, 'N' };                  % Force
    x = { 0, 'm' };                  % Deformation
end

function setup
    if k <= 0
        error('k cannot be less than zero')
    end
end

branches
    f : r.f -> c.f;
end

equations
    v == r.v-c.v;
    f == k*x*x;

end

end

[lilly michel]

When I use simulink to compile the battery model, the following problems always occur： Error compiling Simscape network for model ssc_lithium_cell_2RC_TEST. Caused by: Unable to compile the physical network. Bother me for a long time, hope to get your guidance

Answer 1

[Sebastian Castro]

Yep, you have 3 variables (force, deformation, velocity) but only 2 equations.

The missing one I believe is the one relating the deformation and velocity using the "der" keyword.

v == x.der;

- Sebastian

[Yogesh Badhe]

Thank you very much.

[Sebastian Castro]

No problem... also, if you want to make a quadratic spring, you may want the equation to handle the sign of the deformation:

f == k*x*abs(x);

- Sebastian

Answer 2

[aymen]

Hy i have the same error in the component of mass.

this is the code: nodes M = foundation.thermal.thermal; % :top end

parameters mass = { 1000, 'kg' };

    sp_heat = { 447, 'J/(kg*K)' };   % Specific heat
end

variables % Differential variables T = {value = {300, 'K'}}; % Temperature

    Q = { 0, 'J/s' }; % Heat flow
end

function setup %#simple % Parameter range checking if mass <= 0 pm_error('simscape:GreaterThanZero','Mass') end if sp_heat <= 0 pm_error('simscape:GreaterThanZero','Specific heat') end end

branches Q : M.Q -> *; end

equations T == M.T; Q == mass * sp_heat * T.der; assert(T>0, 'Temperature must be greater than absolute zero') end

end

and this is the error message

['HEV_SeriesParallel/Electrical/System Level/DC-DC Converter/Thermal Model/Thermal Mass']: Type mismatch for equation. The left hand side of the equation is {[1x1 double], 'C'} and the right hand side of the equation is {[1x1 double], 'K'}. T = {[1x1 double], 'C'} M.T = {[1x1 double], 'K'} In foundation.thermal.elements.mass (line 45)