[TTT_IOU]

试试这样：
syms n
T = 20;
m = 500;
k = 100000;
u = 0.01;
L = 5000;
a = 0.5;
g = 9.8;
s = a + 2*n*pi*i/T;
w=0;
for t=1:0.1:10
w=w+1;
F = -k*m*s*u*(m*s*s+2*k)/((m*s*s+k)*(m*s*s+2*k)-k*k)+2*m*g/s;
F1 = -k*m*a*u*(m*a*a+2*k)/((m*a*a+k)*(m*a*a+2*k)-k*k)+2*m*g/a;
s1=real(F*cos(2*n*pi*t/T));
s2=imag(F*sin(2*n*pi*t/T));
s3=real(F1);
f1=symsum(s1,n,1,5000);%%5000的话数值太大，很耗时间的，机子需要时间的
f2=symsum(s2,n,1,5000);
D(w)=2*exp(a*t)*(f1-f2-0.5*s3);
end
t=1:0.1:10;
plot(t,double(D))