norm = sqrt(ax*ax + ay*ay + az*az); //acc?????é????
ax = ax /norm;
ay = ay / norm;
az = az / norm;
// estimated direction of gravity and flux (v and w) ????????·??ò???÷??/±??¨
vx = 2*(q1q3 - q0q2); //????????xyz??±í??
vy = 2*(q0q1 + q2q3);
vz = q0q0 - q1q1 - q2q2 + q3q3 ;
// error is sum of cross product between reference direction of fields and direction measured by sensors
ex = (ay*vz - az*vy) ; //?ò?????????à????????·??????ó??
ey = (az*vx - ax*vz) ;
ez = (ax*vy - ay*vx) ;
exInt = exInt + ex * Ki; //???ó????????·?
eyInt = eyInt + ey * Ki;
ezInt = ezInt + ez * Ki;