负特征值问题

greatchina

请问，为什么求出的D矩阵中存在负值？导致f中存在复数。谢谢

m1=0.162;m2=0.0162;m3=0.0162;m4=0.0162;m5=0.0162;         
m6=0.162;m7=0.0162;m8=0.0162;m9=0.0162;m10=0.0162;
m11=0.162;m12=0.0162;m13=0.0162;m14=0.0162;m15=0.0162;  
m16=0.162;m17=0.0162;m18=0.0162;m19=0.0162;m20=0.0162;
m21=0.162;m22=0.0162;m23=0.0162;m24=0.0162;m25=0.0162;  
m26=0.162;m27=0.0162;m28=0.0162;m29=0.0162;m30=0.0162;
I1=8.733e-7;I2=8.533e-7;I3=8.533e-7;I4=8.533e-7;I5=8.533e-7;               
I6=8.733e-7;I7=8.533e-7;I8=8.533e-7;I9=8.533e-7;I10=8.533e-7;
I11=8.733e-7;I12=8.533e-7;I13=8.533e-7;I14=8.533e-7;I15=8.533e-7;   
I16=8.733e-7;I17=8.533e-7;I18=8.533e-7;I19=8.533e-7;I20=8.533e-7;
I21=8.733e-7;I22=8.533e-7;I23=8.533e-7;I24=8.533e-7;I25=8.533e-7;   
I26=8.733e-7;I27=8.533e-7;I28=8.533e-7;I29=8.533e-7;I30=8.533e-7;
h=15.875e-3;   
m0=1.02;     
T0=100;              
v=10;
T=T0+m0*v^2;            
%质量，刚度矩阵:
M=[(m1+m2)/4+(I1+I2)/h^2,m2/4-I2/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    m2/4-I2/h^2,(m2+m3)/4+(I2+I3)/h^2,m3/4-I3/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,m3/4-I3/h^2,(m3+m4)/4+(I3+I4)/h^2,m4/4-I4/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,m4/4-I4/h^2,(m4+m5)/4+(I4+I5)/h^2,m5/4-I5/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,m5/4-I5/h^2,(m5+m6)/4+(I5+I6)/h^2,m6/4-I6/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,m6/4-I6/h^2,(m6+m7)/4+(I6+I7)/h^2,m7/4-I7/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,m7/4-I7/h^2,(m7+m8)/4+(I7+I8)/h^2,m8/4-I8/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,m8/4-I8/h^2,(m8+m9)/4+(I8+I9)/h^2,m9/4-I9/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,m9/4-I9/h^2,(m9+m10)/4+(I9+I10)/h^2,m10/4-I10/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,m10/4-I10/h^2,(m10+m11)/4+(I10+I11)/h^2,m11/4-I11/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,m11/4-I11/h^2,(m11+m12)/4+(I11+I12)/h^2,m12/4-I12/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,m12/4-I12/h^2,(m12+m13)/4+(I12+I13)/h^2,m13/4-I13/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,m13/4-I13/h^2,(m13+m14)/4+(I13+I14)/h^2,m14/4-I14/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,m14/4-I14/h^2,(m14+m15)/4+(I14+I15)/h^2,m15/4-I15/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,m15/4-I15/h^2,(m15+m16)/4+(I15+I16)/h^2,m16/4-I16/h^2,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,m16/4-I16/h^2,(m16+m17)/4+(I16+I17)/h^2,m17/4-I17/h^2,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m17/4-I17/h^2,(m17+m18)/4+(I17+I18)/h^2,m18/4-I18/h^2,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m18/4-I18/h^2,(m18+m19)/4+(I18+I19)/h^2,m19/4-I19/h^2,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m19/4-I19/h^2,(m19+m20)/4+(I19+I20)/h^2,m20/4-I20/h^2,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m20/4-I20/h^2,(m20+m21)/4+(I20+I21)/h^2,m21/4-I21/h^2,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m21/4-I21/h^2,(m21+m22)/4+(I21+I22)/h^2,m22/4-I22/h^2,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m22/4-I22/h^2,(m22+m23)/4+(I22+I23)/h^2,m23/4-I23/h^2,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m23/4-I23/h^2,(m23+m24)/4+(I23+I24)/h^2,m24/4-I24/h^2,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m24/4-I24/h^2,(m24+m25)/4+(I24+I25)/h^2,m25/4-I25/h^2,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m25/4-I25/h^2,(m25+m26)/4+(I25+I26)/h^2,m26/4-I26/h^2,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m26/4-I26/h^2,(m26+m27)/4+(I26+I27)/h^2,m27/4-I27/h^2,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m27/4-I27/h^2,(m27+m28)/4+(I27+I28)/h^2,m28/4-I28/h^2,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m28/4-I28/h^2,(m28+m29)/4+(I28+I29)/h^2,m29/4-I29/h^2;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m29/4-I29/h^2,(m29+m30)/4+(I29+I30)/h^2];
K=[-(m1*v^2+m2*v^2)/h^2+2*T/h,m2*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    m2*v^2/h^2-T/h,-(m2*v^2+m3*v^2)/h^2+2*T/h,m3*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,m3*v^2/h^2-T/h,-(m3*v^2+m4*v^2)/h^2+2*T/h,m4*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,m4*v^2/h^2-T/h,-(m4*v^2+m5*v^2)/h^2+2*T/h,m5*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,m5*v^2/h^2-T/h,-(m5*v^2+m6*v^2)/h^2+2*T/h,m6*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,m6*v^2/h^2-T/h,-(m6*v^2+m7*v^2)/h^2+2*T/h,m7*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,m7*v^2/h^2-T/h,-(m7*v^2+m8*v^2)/h^2+2*T/h,m8*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,m8*v^2/h^2-T/h,-(m8*v^2+m9*v^2)/h^2+2*T/h,m9*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,m9*v^2/h^2-T/h,-(m9*v^2+m10*v^2)/h^2+2*T/h,m10*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,m10*v^2/h^2-T/h,-(m10*v^2+m11*v^2)/h^2+2*T/h,m11*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,m11*v^2/h^2-T/h,-(m11*v^2+m12*v^2)/h^2+2*T/h,m12*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,m12*v^2/h^2-T/h,-(m12*v^2+m13*v^2)/h^2+2*T/h,m13*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,m13*v^2/h^2-T/h,-(m13*v^2+m14*v^2)/h^2+2*T/h,m14*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,m14*v^2/h^2-T/h,-(m14*v^2+m15*v^2)/h^2+2*T/h,m15*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,m15*v^2/h^2-T/h,-(m15*v^2+m16*v^2)/h^2+2*T/h,m16*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,m16*v^2/h^2-T/h,-(m16*v^2+m17*v^2)/h^2+2*T/h,m17*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m17*v^2/h^2-T/h,-(m17*v^2+m18*v^2)/h^2+2*T/h,m18*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m18*v^2/h^2-T/h,-(m18*v^2+m19*v^2)/h^2+2*T/h,m19*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m19*v^2/h^2-T/h,-(m19*v^2+m20*v^2)/h^2+2*T/h,m20*v^2/h^2-T/h,0,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m20*v^2/h^2-T/h,-(m20*v^2+m21*v^2)/h^2+2*T/h,m21*v^2/h^2-T/h,0,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m21*v^2/h^2-T/h,-(m21*v^2+m22*v^2)/h^2+2*T/h,m22*v^2/h^2-T/h,0,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m22*v^2/h^2-T/h,-(m22*v^2+m23*v^2)/h^2+2*T/h,m23*v^2/h^2-T/h,0,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m23*v^2/h^2-T/h,-(m23*v^2+m24*v^2)/h^2+2*T/h,m24*v^2/h^2-T/h,0,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m24*v^2/h^2-T/h,-(m24*v^2+m25*v^2)/h^2+2*T/h,m25*v^2/h^2-T/h,0,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m25*v^2/h^2-T/h,-(m25*v^2+m26*v^2)/h^2+2*T/h,m26*v^2/h^2-T/h,0,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m26*v^2/h^2-T/h,-(m26*v^2+m27*v^2)/h^2+2*T/h,m27*v^2/h^2-T/h,0,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m27*v^2/h^2-T/h,-(m27*v^2+m28*v^2)/h^2+2*T/h,m28*v^2/h^2-T/h,0;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m28*v^2/h^2-T/h,-(m28*v^2+m29*v^2)/h^2+2*T/h,m29*v^2/h^2-T/h;
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,m29*v^2/h^2-T/h,-(m29*v^2+m30*v^2)/h^2+2*T/h];
[V,D]=eig(K,M);
f=sqrt(D)/(2*pi);

zhuofeng

这程序写的太牛逼了，真佩服丫的

zhuyf

复数就对了
实部是阻尼，虚部是频率