Two calculation models leadind to different results

[fenaux]

Thanks for making this package available

I use Madgwick filter in two different modes first one quat = np.zeros((time_run.size, 4), dtype=np.float64)

"""initialize filter""" madgwick = ahrs.filters.Madgwick(frequency=fs) """ initial state""" quat[0] = np.array([q0[0], q0[1], q0[2], q0[3]]) gyr0=np.zeros(3, dtype=np.float64)

"""For all data""" for t in range(1, time_run.size): quat[t] = madgwick.updateIMU(quat[t-1], gyr=gyr_run[t] * np.pi/180, acc=acc_run[t])

acc_earth = [] gyr_earth = [] for acc_t, gyr_t, q_t in zip(acc_run, gyr_run, quat): acc_earth.append(Quaternion(q_t).rotate(acc_t)) gyr_earth.append(Quaternion(q_t).rotate(gyr_t * np.pi / 180)) acc_earth = np.array(acc_earth) gyr_earth = np.array(gyr_earth) acc_earth -= np.array([0,0,1]) # remove gravity acc_earth *= 9.81 # switch to m/s/s

second one attitude = ahrs.filters.Madgwick(acc=acc_run, gyr=gyr_run * np.pi / 180, q0=q0, fs=fs) acc_2 = [] for acc_t, q_t in zip(acc_run, attitude.Q): acc_2.append( Quaternion(q_t).rotate(acc_t) ) acc_2 = np.array(acc_2) acc_2 -= np.array([0,0,1]) # remove gravity acc_2 *= 9.81 # switch to m/s/s

and results are not the same

as the person wearing the IMU is bending without changing place around 27s, result of mode 2 seems to be more realistic But why are these two modes leading to different results ?