User Manual

close to the (ferro-) magnetic material can the material be considered as disturbing, since

the field lines bend towards the object when in close proximity. For more detailed

information about the influence of magnetic field on orientation, see the PhD thesis “Inertial

and magnetic sensing of human motion” D. Roetenberg 2006

Figure 1: Simulation of ferromagnetic objects in free space with a homogeneous magnetic

field

Homogenous magnetic field

As mentioned above, it is advised to avoid, at least starting a measurement in a highly

disturbed magnetic environment (in a magnetic norm of about 2 or 3). If however, the

measurement begins with a magnetic norm of around 2 or 3, and remains within ±0.2 of this

value, the orientation should remain accurate.

If the homogenous and highly disturbed magnetic field is due to the MTw fixed to an

instrument, or a prosthesis, it is best to carry out magnetic field mapping for this MTw (see

section 7.1). This instructs XKF-3w algorithm that the magnetic field has a new value.

Varying magnetic field

The XKF-3w algorithm can compensate for areas of fast fluctuating magnetic fields.

However, slow, large (>±0.2) changes are more difficult for the algorithm to compensate for,

over periods of time longer than approximately 30s, since the algorithm will constantly be

updating its new heading value.

NOTE:

Do not expose the MTw to very strong magnetic fields. There is a chance the MTw may

become magnetized which will render the calibration values of the magnetic field sensors

.http://www.xsens.com/images/stories/PDF/Inertial%20and%20Magnetic%20Sensing%20of

%20Human%20Motion.pdf

Homogenous

magnetic field

Disturbed

magnetic

field