MTi and MTx User Manual and Tech. Doc., © 2005, Xsens Technologies B.V.
MT0100P.E
7
2.2
Orientation performance specification
Typical performance characteristics of MTi and MTx orientation output.
Dynamic Range
:
all angles in 3D
Angular Resolution
:
0.05
°
RMS
(
2
)
Static Accuracy (roll/pitch):
<0.5
°
Static Accuracy (heading)
(
3
)
:
<1.0
°
Dynamic Accuracy
:
2
°
RMS
(
4
)
Update Rate
:
user settable, max 120 Hz
(
5
)
2.2.1 Sensor fusion algorithm settings
The MTi and MTx has been designed to operate with the highest possible accuracy under a
wide range of operating conditions. Under some circumstances however the performance may
benefit from some of the advanced settings available in the Sensor Fusion Algorithm. Mainly
when transient accelerations are expected it may be attractive to the advanced user, to tweak
or explore the influence of some advanced settings of the algorithm.
NOTE:
Normal operation does not require the user to change these settings.
Weighting factor
Indicates how much the sensor data from the magnetometer should be weighted relative to the
accelerometer data. A number of 1 indicates the magnetometer data is considered equal to the
accelerometer data and this should be the default value. A number of 0.0 will completely
disregard any data from the magnetometers, otherwise valid range is <0.1 ; 10].
Filter Gain
The gain is the most important tweaking option. Very roughly the gain equals the “cross-
over” frequency of the sensor fusion algorithm in Hertz. For example, a value of 1 for the
gain means, more or less, that frequency components of the calculated orientation vector
exceeding 1 Hz will be determined by the rate of turn sensors and components below 1 Hz
will be determined by the accelerometers and magnetometers. The actual implementation is of
course more sophisticated but this serves as an example for understanding.
Valid values are larger than 0.01 and lower than 50, i.e. <0.01 .. 50], some values may lead to
unstable operation of the algorithm under certain conditions.
The recommended default
value of the gain is 1.
Adapt to Magnetic Disturbances
Large amounts of ferrous material (iron, nickel and cobalt but not e.g. aluminum and most
stainless steels) will disturb the homogenous earth magnetic field used as a reference by the
2
1
σ
standard deviation of zero-mean angular random walk
3
in homogenous magnetic environment
4
may depend on type of motion
5
inertial data max update rate is 512 Hz
