calibration for Imu and show gesture
https://blog.csdn.net/shenshikexmu/article/details/80013444
load('calfata.mat')
[Ta,Ka,Ba,Tg,Kg,Bg,Tm2a,Bm,Vm,mag_strength]=ImuCalibration_Gesture(cal_data)
conference A Robust and Easy to implement method for imu calibration without External Equipments
算法mag2acc_matrix假设重力与磁向量的夹角不变，算法Cal_mag4acc_frame利用不同姿态下传感器感受的磁通向量的变化与姿态变化的相关性，计算参数。
conference Nonlinear Complementery Filters on the Special Orthogonal Group
inspired by http://blog.csdn.net/luoshi006/article/details/51513580
derivation A Double-Stage Kalman Filter for Orientation Tracking with an Integrated Processor in 9-D IMU
high and low pass filter to Gyro atitude with Accelerate & Magnetic
