While operating my ADIS16480 I noticed the following strange behavior of the gyroscopes:
- When the system is at rest (sitting on the desk), after SW reset, gyroscopes correctly display very small rotation rates.
- After the system is moved significantly (not "shaken", just moved as it would be in normal operating conditions) and then put back at rest, the gyroscopes constantly indicate some relatively high rotation rates. Since the standard deviation of these values are very small, it seems that the gyroscopes display some high bias values.
- If the system is then tapped (gently, with a finger), the values indicated by the gyroscopes suddenly drop to lower values. The low values typical of rest conditions, however, are achieved only after the system goes through a SW reset.
The following drawing summarizes the situation. The data pertaining to the situation shown are reported in the attached Excel file.
I realize that the abnormal values of the gyroscopes' biases are probably determined by the Kalman filter, that "guesses" them badly. For this reason, I have been double checking the settings of all registers involved with the Kalman estimation, but they seem OK to me... The settings of all registers are reported in the attached TXT file.
One last note: it took me a while to note the high values of the gyroscopes, as the EVAL-ADIS SW displays their (high) values in writing (in the left boxes), but it depicts them as being very close to zero in the diagram (see attached image file).
Thanks everybody for your thoughts !