R = 2;
L = 8e-3;
Ka = 0.2;
J2 = 0.1e-3;
B2 = 50e-6;
N = 5;
J4 = 1e-3;
B4 = 70e-6;

%

A = [-R./L -Ka.*N./L; Ka.*N./(J2.*N.^2 + J4) -(B2.*N.^2 + B4)./(J2.*N.^2 + J4)];
B = [1./L; 0];
C = [0 N; 0 1];
D = [0; 0];

%

sys = ss(A, B, C, D);

%

opt = stepDataOptions('StepAmplitude', 20);
step(sys, opt)