Orientation resolved measurements of accelerations with sensor particles in bioreactors

The measurement of the spatially distributed
flow field in large industrial vessels, e.g. biogas fermenters,
is not possible with commercially available measurement
equipment. Therefore the concept of flow following sensor
particles has been developed. They act as data loggers
within the vessel. The sensor particles are equipped with
a pressure sensor and an inertial measurement unit to
measure their motion. The measurements are taken in
the coordinate frame of the sensor particle and need to
be transformed into the vessel’s coordinate frame to ana-
lyze the flow field. This is done by an error-state Kalman
filter which estimates the orientation of the sensor par-
ticle with respect to the vessel based on the direction
of the gravitational acceleration and the local magnetic
field. Since no other aiding sensors are available or usable
within an industrial vessel particular emphasis was given
to the stochastic modeling of the inertial sensors and the
calibration of the accelerometer. Based on the orienta-
tion estimation, the measured acceleration is transformed
into the vessel frame. We performed two experiments in
a 1.4 m³ lab reactor to qualify this approach. The results
show, that the transformed acceleration is in good quali-
tative agreement with the known flow field inside the lab
reactor