I'm getting a blank graph.

Question

Vishal Antony 2018-10-9

0
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https://ww2.mathworks.cn/matlabcentral/answers/423093-i-m-getting-a-blank-graph

回答： Miriam 2018-10-9

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