Document MT0605P.E
© Xsens Technologies B.V.
MTi User Manual
19
3.3 Xsens sensor fusion algorithm for MTi 100-series
3.3.1
MTi 100-series filter
The Xsens sensor fusion algorithm in the MTi 100-series has several advanced features. It can handle
a multitude of data channels, to incorporate GPS and barometer data as well.
3.3.2
Transient accelerations
The overall accuracy and robustness of the MTi 100-series is significantly higher than the overall
accuracy of the MTi 10-series. The most important factor contributing to this is the use of higher-
accuracy gyroscopes. The gyroscopes in the MTi-100 series are vibration-rejecting, quad-structure
MEMS-gyroscopes. Because of the excellent bias stability it is possible to integrate the rate of turn for
a long time, requiring less frequent reference updates for orientation. The Xsens sensor fusion
algorithm can detect transient accelerations and will use the gyroscopes for a longer time. Next to the
better gyroscopes, the MTi-G-700 algorithm adds robustness to the orientation and position estimates,
making the MTi 100-series the better choice in more demanding applications.
3.3.3
Magnetic distortions
As with transient accelerations, magnetic distortions are also detected by the sensor fusion algorithm
in the MTi 100-series. This makes it possible to use the magnetometers in periods of homogenous
magnetic fields but discarding magnetometer updates when the magnetic field is distorted. Because of
the superior gyroscopes in the MTi 100-series, the heading will be drifting at a relatively low rate.
3.3.4
Loss of GPS
When the MTi-G-700 GPS/INS has limited/mediocre GPS reception or even no GPS reception at all,
the MTi-G-700 sensor fusion algorithm seamlessly adjusts the filter settings in such a way that the
highest possible accuracy is maintained. The GPS status will be monitored continuously so that the
filter can take GPS data into account when available and sufficiently trustworthy. In case loss of GPS
lasts longer than 45-60 seconds (exact time depends on the filter profile), the MTi-G-700 will go into a
state where it no longer uses velocity estimates in the filter.
3.3.5
MTi 100-series filter profiles
Only the MTi-G-700 GPS/INS can use GPS updates; the MTi-300 AHRS and MTi-G-700 GPS/INS use
the magnetometers. The MTi-200 only uses the inertial sensors.
The sensor fusion algorithm uses assumptions about the acceleration and the magnetic field to obtain
orientation. Because the characteristics of the acceleration or magnetic field differ for different
applications, the filter makes use of filter profiles to be able to use the correct assumptions given the
application. This way, the filter can be optimized for different types of movement. For optimal
performance, the correct filter profile must be set by the user.
Number
Name
IMU
Magnetometer
Product
39
General
•
•
300-AHRS
40
High_mag_dep
•
•
300-AHRS
41
Dynamic
•
•
300-AHRS
42
Low_mag_dep
•
•
300-AHRS
43
VRU_general
•
300-AHRS, 200-VRU
