clear all
clc
syms x;
f=(-5.324e-15*x^7)+(-8.452e-12*x^6)+(-5.204e-9*x^5)+(-1.558e-6*x^4)+(-0.0002253*x^3)+(-0.01515*x^2)+(-1.464*x)+222.9;
f1=diff(f);
f2=diff(f1);
g=(1+f1^2)^(3/2)/abs(f2);
F=@(x)eval(g);
[X,fval]=fminbnd(F,0,2)%X为最小曲率半径事的x的值,fval为最小曲率半径

自变量的范围要给出来啊

clear all
clc
syms x;

f=(-5.324e-15*x^7)+(-8.452e-12*x^6)+(-5.204e-9*x^5)+(-1.558e-6*x^4)+(-0.0002253*x^3)+(-0.01515*x^2)+(-1.464*x)+222.9;
ezplot(f,[-500 0])
f1=diff(f);
f2=diff(f1);
g=(1+f1^2)^(3/2)/abs(f2)
F=@(x)(eval(g));
[X,fval]=fminbnd(F,-500,0)

另外根据计算的结果最小曲率并不在顶点处，可提高拟合的阶次来降低误差