Navigation System

The navigation system of the nanoAUV is based on a sensor fusion using an „Unscented Kalman Filter“ (UKF). According to the current concept, the following sensors will be installed in the nanoAUV:

  • Sensonor STIM 300 Inertial Measurement Unit (IMU): measures accelerations and rotation rates to determine the three-dimensional attitude (roll, pitch and heading)
  • Multiple PNI RM3100 Magnetometers: measures the magnetic field to determine the nanoAUV’s heading with respect to magnetic north of the celestial body (compass)
  • RBRoem P Absolute Pressure Sensor: measures the absolute water pressure to determine the depth of the nanoAUV within the water column
  • EvoLogics OEM USBL: measures the nanoAUV’s position by determining the travel times and directions of acoustic signals
  • WaterLinked Doppler Velocity Log A50 (DVL): measures the Doppler shift of acoustic signals over ground or ice to determine the relative velocity
Preliminary design of the navigation sensor suite for the nanoAUV (Credits: Sebastian Meckel/MARUM, EvoLogics GmbH, Sensonor, KELLER AG, PNI, WaterLinked).

With the help of these sensors, a fused navigation solution is estimated for the nanoAUV. This consists of three-dimensional position, velocity and the attitude. In addition, other states such as errors of the IMU and the water current are estimated. The subject of current discussion is whether to install a Waterlinked DVL A50 for velocity measurement in the nanoAUV. Due to the large installation volume and energy consumption, it is being investigated whether the DVL can be dispensed and if a safe and long-term stable navigation remains still possible. An alternative is to measure the dynamic pressure at several points on the bow of the nanoAUV (pressure speedometer).