Reuse of Modified Classes

The class concept is the key to reusing modeling knowledge in Modelica. Assume that we would like to connect two filter models in series. Instead of creating two separate filter classes it is better to define a common filter class and create two instances of this class, which are connected.

model LowPassFilter parameter Real T = 1; Real u, y(start = 1,fixed=true); equation T*der(y) + y = u; end LowPassFilter;

The LowPassFilter class can be used to create two separate instances of the filter and connect them by using the equation F2.u = F1.y.

model FiltersInSeries LowPassFilter F1(T = 2), F2(T = 3); equation F1.u = sin(time); F2.u = F1.y; end FiltersInSeries;

FiltersInSeries can be used to declare variables at a higher hierarchical level.

model ModifiedFiltersInSeries FiltersInSeries F12(F1(T = 6), F2.T = 11); end ModifiedFiltersInSeries;

1 Simulation of FiltersInSeries and ModifiedFiltersInSeries

simulate( FiltersInSeries )
plot({F2.u,F1.u})

simulate( ModifiedFiltersInSeries )
plot({F12.F1.T,F12.F1.u})