matlab中使用fminsearch函数,如何限定自变量的取值范围?

f=@(K)(K(1)/2 + (4*K(5))/5 + (4*K(6))/5 - 36568701964855/34359738368)^2 + (K(4)/8 - 4053796115654203/281474976710656)^2 + (K(4)/8 - 210)^2 + (K(5)/5 - 650)^2 + (K(6)/5 - 275)^2 + (K(6)/5 - 6859982151351983/281474976710656)^2 + (K(5)/5 - 7332050830254413/35184372088832)^2 + (K(3)/8 + K(4)/8 + K(5)/20 - 379958236369475/549755813888)^2 + (K(2)/8 + K(4)/8 + K(6)/20 - 4850177850251011/17592186044416)^2;

[K,fval]=fminsearch(f,[1,1,1,1,1,1])

我想让K1—K6都是正数，没有金币了，好心人帮帮忙！感激不尽！