I have a 4DOF, forced, damped linearized system. I trying to calculate the the forced response of the system. I'm getting the numerical values, I have checked this by printing the matrices. But I'm getting a blank graph. Below is the code I have written.
function forcedResponse kxx = 200e6; kyy = 150e6; kxy = 15e6; kyx = 10e6; cxx = 200e3; cyy = 150e3; cyx = 13e3; cxy = 18e3; l = 1; d = 0.05; rho = 7800; ez = 0.001; e = 0.0001; m = 0.25*pi*d^2*l*rho; Id = (m/12)*(0.75*d^2 + l^2); M = [m 0 0 0 0 m 0 0 0 0 Id 0 0 0 0 Id]; C = [2*cxx 2*cxy 0 0 2*cyx 2*cyy 0 0 0 0 0.5*l^2*cxx 0.5*l^2*cxy 0 0 0.5*l^2*cyx 0.5*l^2*cyy]; K = [2*kxx 2*kxy 0 0 2*kyx 2*kyy 0 0 0 0 0.5*l^2*kxx 0.5*l^2*kxy 0 0 0.5*l^2*kyx 0.5*l^2*kyy]; hold on; for w = 1:10 % w is angular speed
D = -w^2*M + 1i*w*C + K % D is 4by4 matrix, M is mass matrix, C is damping matrix, K is stiffness matrix
Fx = m*e*w^2; Fy = -1i*m*e*w^2; Mxz = m*e*w^2*ez; Myz = -1i*m*e*w^2*ez; F = [Fx; Fy; Mxz; Myz]; %force amplititude. It's 4by1 vector
X = D\F; %displacement amplitude. contains complex elements
plot(w,abs(X(1))) end xlabel('spin speed (rad/s)'), ylabel('Amplitude of translational displacement (m)') title('X v \omega') end
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