5.6 Example: Filtering the Rotation Angle of a Phone

Here is a plot of estimated angle of rotation in the X-axis direction based on both the accelerometer and integration of the gyroscope measurements.


Recall that the phone was not moving at all, and so the gyro should not really be recording any motion. However, natural noise in the instrument produces some variation over time. In particular, there appears to be a slight negative bias, so that the gyro appears to think it is being rotated slightly in the negative direction. When this negative bias is integrated over time, its impact accumulates over time, as is shown in the previous figure.