The Autonomous Redundant Navigation System of an AUV for Mine ...

4 MARPOSII navigation system of the SEA
OTTER MK2 AUV.
MARPOSII, the successor of MARPOS [1], is the
real-time embedded equivalent of the offline
NAVBOX tool. Key features are:
• High performance Doppler-inertial dead
reckoning based navigation.
• Redundant hardware, software and algorithms
- any single point failure is managed.
• Calibration and post-processing package
based on optimal smoothing (option).
• Combined Synthetic LBL [2] and SLAM for
long-term covert autonomous navigation
with bounded error and superior relocation
accuracy (option).
4.1 Hardware configuration
• Navigation grade IMU (CEPR < 1NMPH)
• DVL: Teledyne RDI Workhorse navigator
• Spread spectrum (wideband) acoustic transceiver:
Sonardyne Ltd. AVTRAK MK2
• Redundancy: Processors, interfaces, power
supply, sensors and algorithms.
• GPS, CTD / SVS, fluxgate, pressure sensor
• OCXO based time system.
Drift < 0.1 second per 24 hours, supported
by GPS 1PPS.
• High performance, low power floating point
processor, Figure 13
Figure 13 Redundant PowerPC based floatingpoint
processors
It is planned to use the ATLAS MARIDAN SEA
OTTER MK1 (M600) AUV (Figure 14) owned and
operated by WTD71 in Eckerförde, Germany for further
MARPOSII development and experimental validation.
Figure 14: M63 M600 Type AUV Operated by
WTD71, Eckernförde, Germany
4.2 Software configuration
• Real-time Kernel.
• Dual processor boards - dual navigation
software packages.
• Flexible messaging system and CORBA [7]
support.
5 Summary
The power and versatility of AINS and the
NAVBOX simulation and post-processing tool were
described. Recorded AUV navigation data were used
to give a practical demonstration and detailed discussion
of the two "unconventional" navigation concepts
"Synthetic LBL" and SLAM. The Synthetic LBL
concept was found to provide superior integrity and
very good autonomous navigation performance. The
efficiency of optimal smoothing for offline improvement
of navigation accuracy was shown and key features
of the MARPOSII real-time embedded navigation
system were listed.
The solid and versatile basis provided by NAVBOX
and MARPOSII means that present and future navigation
system requirements will be met.
6 Acknowledgments
The NAVBOX AINS simulation and post-processing
tool was developed largely within the AUV 2000
project of the German Federal Office of Defence
Technology and Procurement (BWB).
The author wishes to thank past and present colleagues
for their contributions, first and foremost
Morten Soede Nielsen and Per Fogt Nielsen of
ATLAS MARIDAN and Ursula Hölscher-Höbing of
ATLAS Elektronik.
The author would also like to thank the skilled members
of the DeBeers Marine AUV team for rewarding
co-operation.