Fault tolerant actuation for dorado class, AUVS.
2009
This paper describes a new control surface actuating design for the Monterey
Bay Aquarium Research Institute (MBARI) Dorado class AUVs. The intent was
to increase reliability as part of obtaining the goal to greatly increase access to
the Arctic Ocean. The new actuating mechanism is part of creating a robust and
economical solution towards increased reliability and fault tolerance. Specifically,
as part of developing the ALTEX Autonomous Underwater Vehicle (AUV) for Arctic
research with basin scale endurance, the concept for under ice missions was redundancy
in critical areas. As the development of the DORADO systems progressed from
the original ALTEX concepts, added drivers came from the operations group looking
for more useable volume in the aft section.
The DORADO vehicle is guided using an articulated tail steering section. The tail
is comprised of a ducted propeller acting as control surfaces and propulsion, in
contrast with the more traditional fin control surfaces used by most vehicles. This
approach was taken to be more robust to impacts as experience using Odyssey IB
vehicles showed the control surfaces damaged during launch and recovery were
the number one failure by far. As predicted by analysis the design also improved
propulsion efficiency. Also worth noting is that this entire tail system stays inside the
21” diameter of the main vehicle body. The new system being developed is unique
in that it keeps all of the key propulsion and actuators but eliminates the current
gimbaled tail through the use of what we refer to as a false center. While several new
components are being developed, the objective is to leverage the existing technology
to the degree possible and allow for an inexpensive as well as direct swap into
existing systems.
The new steering mechanism uses a Three Actuator False Center Control solution.
The design was first modeled and tested for feasibility. After passing the preliminaries,
the decision was made to build a full-scale sea going unit. We now have that
system built and in bench testing, ready to swap in for at sea testing in the very near
future. We’ve already demonstrated that the new design offers a superior use of
space yielding more useable volume for other equipment. The model demonstrated
the added redundancy that we will duplicate at sea. We believe the design is very
robust and has a broad range of uses in long duration unattended operations where
fault situations must be dealt with by the autonomous system. In this paper we will
discuss our progress to date, our current test efforts, and the near term future uses of
this new control section for DORADO science vehicles.
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