User Manual

individual device calibration

values on the embedded microprocessor (MCU) of the MTw.

Based on this data the MTw further calculates velocity increments and orientation

increments using an SDI algorithm. The main advantage of using the SDI algorithm is that full

3D tracking accuracy can be maintained even if the output update rate from the MTw is very

low (<100 Hz). An additional advantage is that the MTw can continue to track the 3D motion

internally when facing transient data loss in the RF transmission and immediately report the

full 3D velocity and orientation increment as soon as the RF link is restored (data packets

again received by the Awinda Station), without the need to re-transmit all the data that was

lost which would a) cause a large delay during real-time tracking b) use a lot of precious RF

bandwidth and consume unnecessary power. The specific use of SDI data in combination

with such a specialized RF protocol, Xsens has named the Awinda protocol

NOTE: Velocity and orientation increments resulting from the embedded SDI can easily be

converted back to acceleration and angular velocity values. At high enough update rates

there is no or negligible loss of accuracy due to this conversion. What is “high enough” is

partly also determined by the dynamics of the movement. Xsens recommends the use of SDI

values rather than acceleration and angular velocity values for further calculations as they

represent the highest degree of accuracy.

The devices are calibrated at the factory by Xsens and is a highly sophisticated process

compensating for component errors that are not stochastic (i.e. they can be modeled).

Compensation models include bias, gain, misalignment, g sensitivity, temperature effects,

etc.

Patents pending.