The MVN motion capture system consists of 17 MTx
sensors with two Xbus Masters [11]. The MTx is an inertial
and magnetic measurement unit and comprises 3D gyroscopes,
3D accelerometers and 3D magnetometers (38×53×21 mm,
30 g). The sensor modules are daisy chained connected to
the Xbus Masters, meaning that there is only one cable
leading to each limb. The Xbus Masters synchronizes all
sensor sampling, provides sensors with power and handles the
wireless communication with the PC or laptop. For quick and
convenient placement, the sensors and cables are integrated in
a Lycra suit and the Xbus Masters are mounted on the back.
The total weight of the system (including 8 AA batteries) is
1.9 kg. Sensor modules are placed on the feet, lower legs,
upper legs, pelvis, shoulders, sternum, head, upper arms, fore
arms and hands (see Figure 1).
When attaching sensors to a body, the initial pose between
the sensors and body segments is unknown. Moreover, the
assessment of distances between body segments is difficult by
numerical integration of acceleration because of the unknown
initial position. Therefore, a calibration procedure has to be
performed in which the sensor to body alignment and body
dimensions are determined (Section II-B).