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Document MT0605P.2018.E
© Xsens Technologies B.V.
MTi User Manual
Table 7: Orientation performance specification
Quantity Condition
MTi-20
VRU
MTi-30
AHRS
MTi-200
VRU
MTi-300
AHRS
MTi-G-710
GNSS/INS
Roll/Pitch
Static
0.2º
0.2º
0.2º
0.2º
0.2º
Dynamic
0.5º
0.5º
0.3º
0.3º
0.3º
Yaw
-
Unreferenced
1.0
Unreferenced
1.0º
0.8º
All specifications listed in Table 7 are based on typical application scenarios.
The performance specifications in this chapter are subject to the following assumptions (see also
footnotes);
Correct filter profile:
If an unsuitable filter profile is chosen, the sensor fusion algorithm will
use erroneous assumptions. Depending on the specific situation this can lead to large errors or
even instability of the filter. Take care to select the correct filter profile. If you are uncertain, do
not hesitate to contact Xsens or your local distributor.
Magnetic distortions:
In several filter profiles the on-board 3D magnetometer is used to
observe the heading. It is assumed that a magnetic field mapping is performed and that the
magnetometers are not distorted by nearby ferromagnetic materials in the environment.
Long-lasting accelerations (all, except for MTi-G-710)
: Each filter profile copes different with
long-lasting accelerations. Although the MTi’s are able to discard these transient accelerations,
they will have an effect after a certain period of time. In the MTi 10-series, this period is shorter
than in the MTi-100 series. The MTi-G-710 with a good GNSS fix can compensate for these
long-lasting accelerations.
Settling time:
Parameters in the MTi’s such as the rate gyro bias or the pressure at sea level
are continuously estimated. The sensor fusion algorithms need some time to estimate such
parameters. Depending on the time since last calibration of the MTi’s, the chosen filter profile
and the quality of the GNSS fix this can take up to 5 minutes. There is no need to have the MTi’s
static during the settling time, on the contrary, movement (accelerations, turns) of the MTi’s will
help to estimate for example the gyro bias quicker as they become observable.
Good GNSS fix (MTi-G-710 only):
o
If there is no GNSS fix the position estimates based on the IMU will degrade very rapidly
(in the order of a few seconds).
o
If there is no GNSS fix the MTi-G cannot calculate correct attitude and heading under
all dynamic conditions due to “apparent gravity” (e.g. centripetal and linear
accelerations). Based on the rate gyros the attitude and heading estimates will degrade
slowly. Attitude accuracy will be the same as the accuracy of an MTi-300. The heading
will typically drift up to a degree every minute.
Valid holonomic constraints (MTi-G-710 only)
: In the Automotive filter profiles of the MTi-G-
710 it is assumed that the x-axis of the MTi-G is mounted in the driving direction of the vehicle.
Accuracy of the heading estimate improves as the alignment error decreases and vice-versa.
Barometric conditions (MTi 100-series only):
In some of the filter profiles, the altitude of the
MTi-G-700/710 is partly estimated by the on-board barometer. It is assumed that the pressure
near the MTi-G reflects the atmospheric pressure outside of the vehicle. So, if you selected a
filter profile that uses barometer data, the MTi-G cannot be used in e.g. a pressurized cabin.
Furthermore, the height accuracy may reduce with very rapid changes in atmospheric pressure
that could occur in e.g. severe thunderstorms.
5.4 Position and velocity performance specification (MTi-G-710)
