StateSpaceModel[{(Subscript[x, 1])'[t]==(Subscript[x, 1])[t]+u[t],(Subscript[x, 2])[t]-0.4(Subscript[x, 1])[t]==0},{(Subscript[x, 1])[t],(Subscript[x, 2])[t]},{u[t]},(Subscript[x, 1])[t],t]

StateSpaceModel[{(({{1, 0}, {-2, -1}})),(({{1}, {2}})),(({{-1, 0}})),(({{0.5}})),(({{1, 0}, {0, 0}}))}]

StateSpaceModel[(TransferFunctionModel[(((s^2)+4)/(s+1)), ])]

StateSpaceModel[{(({{a}})),(({{b}})),(({{c}})),(({{d}})),(({{e}}))},SamplingPeriod->τ]

ControllableModelQ[(StateSpaceModel[1, 0, -1, 0, 1, 0, 0, 0, -2, 1, 0, 1, 0, ])]

StateSpaceModel[(StateSpaceModel[e, a, b, c, d, ]), DescriptorStateSpace->False]