Document MT0605P.E
© Xsens Technologies B.V.
MTi User Manual
30
4.3 Orientation performance specification
In the MTi product portfolio, several products provide roll, pitch and (un)stabilized yaw. The table
below provides an overview of the specific products and orientation performances. The 10-IMU and
the 100-IMU are not listed, as they do not provide orientation.
Typical orientation errors are in 1
σ
RMS values; maximum errors are in degrees. Note that the
validation tests can be found in the Technical Datasheet (document MT0503P, [MTI_TD]). For yaw,
maximum errors cannot be provided, as this strongly depends on the environmental conditions.
MTi-20
VRU
MTi-30
AHRS
MTi-200
VRU
MTi-300
AHRS
MTi-G-700
GPS/INS
Typ
Max
Typ
Max
Typ
Max
Typ
Max
Typ
Max
Roll/Pitch
Static
5
0.2º
0.4º
0.2º
0.4º
0.2º
0.25º
0.2º
0.25º
0.2º
0.25º
Dynamic
0.5º
2.0º
0.5º
2.0º
0.3º
1.0º
0.3º
1.0º
0.3º
1.0º
Yaw
6
Unref.
1.0
N/A
Unref.
1.0º
N/A
1.0º N/A
Performance specifications highly depend on the conditions. The MTi Technical Datasheet [MTI_TD],
containing validation tests and more details on the specifications of orientation and individual sensors,
is available. The orientation performance of the MTi-G-700 is valid in an increased range of
applications and motions.
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-700)
: every 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-700 with a good GPS 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 GPS fix this can take up to 15 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 GPS fix (MTi-G-700 only):
o
If there is no GPS fix the position estimates based on the IMU will degrade very
rapidly (in the order of a few seconds).
o
If there is no GPS fix the MTi-G cannot calculate correct attitude and heading under
all dynamic conditions due to “apparent gravity” (e.g. centripetal and linear
5
Max error with respect to earth coordinate system
6
MTi-20 VRU and MTi-200 VRU: unreferenced (heading is yaw rate of gyroscopes)
