function q = Rv2Quat(rv)  
%旋轉(zhuǎn)矢量轉(zhuǎn)化為變換四元數(shù)
	norm = sqrt(rv'*rv);
    if norm>1.e-20
        f = sin(norm/2)/(norm/2);
    else
        f = 1;
    end
    q = [cos(norm/2); f/2*rv];