Publications

We have developed a method for a Tethys-class long-range autonomous underwater vehicle (LRAUV) (which has a propeller and a buoyancy engine) to track a targeted isothermal layer (within a narrow temperature range) in a stratified water column when operating in buoyancy-controlled drift mode.

The method presented here estimates the location of a submerged asset using a single one-way acoustic ping, without synchronized clocks.

LRAUV Tethys encountered a white shark in northern Monterey Bay. The shark left left bite grooves in the pressure vessel and tooth fragments embedded in the aft fairing. This article reviews the vehicle motion during the strike and the effects of the damage afterward.

We derive a stable identifier to estimate rotations using rotors in Geometric Algebra and apply it to a navigation problem on an underwater vehicle in the field.

This paper presents the development effort toward demonstrating acoustic tracking and homing with a long-range AUV (LRAUV) at the Monterey Bay Aquarium Research Institute (MBARI). The acoustic tracking system uses a directional acoustic transponder (DAT) from Teledyne Benthos, backed by an acoustic baffle made from syntactic acoustic damping material (SADM). We discuss sensor integration into the LRAUV system, procedures and results from an in-house calibration, and field tests with both anchored and towed transponders.

We present a novel approach using singular value decomposition to decouple the spatial and temporal components, interpolate them independently, and reconstruct the original field on an as-needed basis.

This dissertation presents three separate – but related – contributions to the art of underwater navigation.

This paper uses rotors in Geometric Algebra to formulate a stable adaptive identifier on the group of rigid body rotations. This identifier is intended to estimate the alignment offsets between independent sensors. The approach provides a straightforward geometric interpretation based on first-order rotor kinematics. Lyapunov theory is used to prove the stability of the identifier, and numerical simulations illustrate its behavior with and without measurement noise.

Measurement delays are inheient in position feedback methods used fot undeiwatei navigation. Even foi small delays, ptopei treatment of these measurements will provide mote lobnst performance and reduce uncertainties, improving overall precision. The Kalman filter (KF) can be adapted to treat delayed measurements in an efficient and mathematically rigorous way. We present a delayed state sigma point Kalman filter (SPKF) implementation for underwater navigation using delayed position measurements. The implementation includes a novel model-based approach to fusing the delayed measurements, with the ability to handle varying delays. We provide an example mission scenario where a surface tender with an ultra-short baseline (USBL) system tracks a submerged vehicle. We use this example to renavigate field data from recent deployments of the National Deep Submergence Facility (NDSF) autonomous underwater vehicle (AUV) Sentry, and compare estimates from a delay-compensated filter to those from a filter that ignores the delay.

An old sea turtle teaches a young engineer about swimming

Two complementary studies examine the performance of three-dimensional hydrofoils based on the pectoral flippers of the Humpback whale. The first study uses a static foil, with application to conventional control surfaces on marine vehicles. The second study uses a dynamic foil, with application to flapping foil propulsion.

We performed Particle Imaging Velocimetry (PIV) on the flow around two static foils in a water tunnel for a range of attack angles.