quaternion.m

大气层内航天器飞行动力学matlab仿真模型

% Copyright Ashish Tewari (c) 2006
function q=quaternion(C)
T=trace(C);
qsq=[1+2*C(1,1)-T;1+2*C(2,2)-T;1+2*C(3,3)-T;1+T]/4;
[x,i]=max(qsq);
if i==4
    q(4)=sqrt(x);
    q(1)=(C(2,3)-C(3,2))/(4*q(4));
    q(2)=(C(3,1)-C(1,3))/(4*q(4));
    q(3)=(C(1,2)-C(2,1))/(4*q(4));
end
if i==3
    q(3)=sqrt(x);
    q(1)=(C(1,3)+C(3,1))/(4*q(3));
    q(2)=(C(3,2)+C(2,3))/(4*q(3));
    q(4)=(C(1,2)-C(2,1))/(4*q(3));
end
if i==2
    q(2)=sqrt(x);
    q(1)=(C(1,2)+C(2,1))/(4*q(2));
    q(3)=(C(3,2)+C(2,3))/(4*q(2));
    q(4)=(C(3,1)-C(1,3))/(4*q(2));
end
if i==1
    q(1)=sqrt(x);
    q(2)=(C(1,2)+C(2,1))/(4*q(1));
    q(3)=(C(1,3)+C(3,1))/(4*q(1));
    q(4)=(C(2,3)-C(3,2))/(4*q(1));
end