[Complementary filter] Adding and subtracting the update component from acc, mag

[wgrand]

Can someone explain to me what the following does? I expected that the quaternion would be a sum of the propagated attitude (from the gyro) and the estimated attitude (from the accelerometer and magnetometer). Why is the latter subtracted when the norm of the two is less than sqrt(2)?

ahrs/ahrs/filters/complementary.py

Lines 315 to 318 in 9e02c5d

	if np.linalg.norm(q_omega + q_am) < np.sqrt(2):
	q = (1.0 - self.gain)*q_omega - self.gain*q_am
	else:
	q = (1.0 - self.gain)*q_omega + self.gain*q_am