Henry Leinhos

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Active sound cancellation system for time-varying signals

US Statutory Invention Registration H1357

Propulsion efficiency of bodies appended with multiple flapping fins: When more is less

Physics of Fluids, 2013

ABSTRACT Underwater animals propel themselves by flapping their pectoral and caudal fins in a nar... more ABSTRACT Underwater animals propel themselves by flapping their pectoral and caudal fins in a narrow range of frequencies, given by Strouhal number St, to produce transitional vortex jets (St is generally expressed non-dimensionally as the product of flapping frequency and stroke (arc) length divided by forward speed). The organized nature of the selection of St and of the vortex jet is thought to maximize hydrodynamic efficiency, although the exact mechanism is not known. Our recent Stuart-Landau equation models, which have self-regulation properties, indicate that the fin and its jet vortices couple. Temporal maps of forces in single isolated fins show a bimodal behavior in certain ranges of the transitional Reynolds number; this behavior bears resemblance to neural bifurcation properties that owe their origin to the self-regulation mechanism. In view of our theoretical and biorobotic evidence of self-regulation in single flapping fins, we explore if this property is altered in a fin-appended body, the goal being to understand how the narrow selection of St, self-regulation, and maximization of hydrodynamic efficiency are related. Swimming vehicles of 1-m scale have been built where a rigid cylindrical body is appended with six flapping fins, three at each end. The fins are rigid, have a rounded leading edge and a laminar section (NACA 0012), and are hinged at one end. The planform is an abstracted version of the penguin wing; it has low aspect ratio and a chord Reynolds number that varies in the transitional range from 10 000 to 60 000. The fin geometry, Reynolds number range, and the nonflexible nature of the main body are in common with those in penguins, and the length and displacement volume are similar to those of sharks. The maximum hydrodynamic efficiency of the fin-appended body (0.40) is lower than that of the single fin (0.57), but is close to that of a fish using several fins. The propulsion density (kW/m3 of displacement volume) of the fin-appended cylinder is similar to that of a cruising shark. If we allow comparison of electrical versus thermal measurements, the total efficiency of the fin-appended body is similar to that of the damselfly and dragonfly, which are also based on vortex propulsion. The fin force fluctuations are modeled by a van der Pol oscillator. Measured phase maps of force fluctuation versus its time derivative correlate with the Strouhal numbers. Until stabilization, the maximum hydrodynamic efficiency of the fin-appended body increases with fin Reynolds number in a staircase pattern whose boundaries correlate with similar transitional sub-regimes in single fins, including the bimodal sub-regimes, thereby relating efficiency with the self-regulating jet vortex oscillators. At low Reynolds numbers, the peak of hydrodynamic efficiency remains flat over a wide range of St, becoming steeper at higher Reynolds numbers with the maximum occurring at lower values of St. The modeling shows that for self-regulation, future biorobotic design should focus on the reduction of structural damping and on a fin-body assembly that has reciprocal energetic interaction with the shed vortex.

Block-adaptive decision feedback equalization with integral error correction for underwater acoustic communications

OCEANS 2000 MTS/IEEE Conference and Exhibition. Conference Proceedings (Cat. No.00CH37158), 2000

This paper presents recent experimental results for an underwater acoustic communications receive... more This paper presents recent experimental results for an underwater acoustic communications receiver based on a block-adaptive implementation of a decision feedback equalizer (DFE). Block-encoded QPSK acoustic data was transmitted from a moving UUV to a stationary platform. The receiver algorithm implemented soft decision decoding within the equalizer decision feedback loop in order to intercept decision errors and improve low SNR performance. Block adaptation of the the DFE was achieved with a Block Recursive Least Squares adaptive mechanism coupled with an integral phase tracking loop. A quaternary block code was used in this case to facilitate receiver implementation such that block decoding was done directly on the QPSK data symbols. Results from Narragansett Bay, Rhode Island show approximately 3 dB performance improvement over a non-coded system.

Handedness helps homing in swimming and flying animals

Scientific Reports, 2013

Swimming and flying animals rely on their ability to home on mobile targets. In some fish, physio... more Swimming and flying animals rely on their ability to home on mobile targets. In some fish, physiological handedness and homing correlate, and dolphins exhibit handedness in their listening response. Here, we explore theoretically whether the actuators, sensors, and controllers in these animals follow similar laws of self-regulation, and how handedness affects homing. We find that the acoustic sensor (combined hydrophone-accelerometer) response maps are similar to fin force maps-modeled by Stuart-Landau oscillators-allowing localization by transitional vortex-propelled animals. The planar trajectories of bats in a room filled with obstacles are approximately reproduced by the states of a pair of strong and weak olivo-cerebellar oscillators. The stereoscopy of handedness reduces ambiguity near a mobile target, resulting in accelerated homing compared to even-handedness. Our results demonstrate how vortex-propelled animals may be localizing each other and circumventing obstacles in changing environments. Handedness could be useful in time-critical robot-assisted rescues in hazardous environments.

format_quoteFish lateral line sensors integrate sound pressure and fluid acceleration to locate and track other vortex-propelled species effectively.format_quote

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Synthesis and Coordination of the Motion of Multiple Flapping Foils for Control of a Biorobotic AUV

OCEANS 2006 - Asia Pacific, 2006

Page 1. Synthesis and Coordination of the Motion of Multiple Flapping Foils for Control of a Bior... more

Dolphin-inspired combined maneuvering and pinging for short-distance echolocation

The Journal of the Acoustical Society of America, 2008

The biorobotic emulation of swimming and flying animals carrying out short-distance echolocation ... more The biorobotic emulation of swimming and flying animals carrying out short-distance echolocation while maneuvering is considered. A simple and lightweight sonar for use on a small, maneuverable underwater vehicle for short-distance echolocation is explored. This sonar has four sensors and uses broadband, high-frequency signals to echolocate. The frequency-time characteristics of these signals are compared to those of bats and dolphins. The biosonar is paired with a biologically inspired, maneuverable, underwater vehicle, the combined use of sensors and maneuverability being analogous to animal behavior. Homing experiments have been carried out in an acoustic test facility where identification and localization of multiple targets is based on fusion of acoustic returns from multiple pings.

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Unified Scaling for Flapping Fins

IEEE Journal of Oceanic Engineering, 2013

ABSTRACT Conventional scaling for steady-fin or flapping-fin forces in a uniform flow is by defin... more ABSTRACT Conventional scaling for steady-fin or flapping-fin forces in a uniform flow is by definition incompatible with the scaling that has been developed for hovering flapping fins. Most flapping-fin-based vehicles will need to operate in all three operating regimes: fixed fin in cruise, flapping in cruise, and flapping in hover. A unified normalization scheme is proposed to enable smooth and optimal transition of the scaling rules between these regimes. A rigid flapping foil was experimentally tested in a towing tank. The generated side force was found to be a function only of the fin bias angle and the vector magnitude of the inflow and flapping speeds. The thrust was found to be a function of the ratio of fin flapping speed to total speed magnitude in addition to bias and speed magnitude. As an application of this scaling, an algorithm to synthesize the foil motion parameters for a desired thrust and side force regardless of vehicle speed was tested experimentally on a single foil in real time.

Capacity calculations for rapidly fading communications channels

IEEE Journal of Oceanic Engineering, 1996

This paper derives an upper bound for the Shannon channel capacity-cost function for a class of r... more This paper derives an upper bound for the Shannon channel capacity-cost function for a class of randomly timevarying channels under an average power constraint. The channels considered can be characterized by a series of uncorrelated parallel diversity channels with Gaussian-distributed random gain and additive white Gaussian noise parameters. The resulting expression for the single-channel case clearly shows that such channels have finite capacity even when the source power is unconstrained. Extensions are made to the multiple-diversitychannel case with a modified "water-filling'' problem resulting.

format_quoteExamining the capacity-cost function under Gaussian gain reveals significant insights into the performance of channels with random scatterers.format_quote

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Open-Loop Control of a Multifin Biorobotic Rigid Underwater Vehicle

IEEE Journal of Oceanic Engineering, 2008

This paper presents an open-loop control system for a new experimental vehicle, named the biorobo... more This paper presents an open-loop control system for a new experimental vehicle, named the biorobotic autonomous underwater vehicle (BAUV). The rigid cylindrical hull of the vehicle is attached with six strategically located fins to produce forces and moments in all orthogonal directions and axes with minimal redundancy. The fins are penguin-wing inspired and they implement the unsteady high-lift principle found widely in swimming and flying animals. The goal has been to design an underwater vehicle that is highly maneuverable by taking the inspiration from nature where unsteady hydrodynamic principles of lift generation and the phase synchronization of fins are common. We use cycle-averaged experimental data to analyze the hydrodynamic forces and moments produced by a single foil as a function of its kinematic motion parameters. Given this analysis, we describe a method for synthesizing and coordinating the sinusoidal motion of all six foils to produce any desired resultant mean force and moment vectors on the vehicle. The mathematics behind the resulting algorithm is elegant and effective, yielding compact and efficient implementation code. The solution method also considers and accommodates the inherent physical constraints of the foil actuators. We present laboratory experimental results that demonstrate the solution method and the vehicle's resulting high maneuverability. Index Terms-Autonomous underwater vehicle (AUV), biorobotics, high lift, maneuverability, open-loop control. I. INTRODUCTION N ATURAL flyers and swimmers have evolved to skillfully utilize physical principles from unsteady hydrodynamics to achieve high maneuverability and efficiency [1]-[6]. Manmade autonomous underwater vehicles (AUVs), on the other hand, have been conceived and operated for decades to either remain safely within the realm of steady hydrodynamics-where the design of vehicle body, actuation mechanisms, and control system is simpler to understand and implement-or to avoid the issue altogether by using a number of thrusters to push an arbitrarily shaped body through the water. This has often resulted Manuscript

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Turning of a Short-Length Cable Using Flapping Fin Propulsion

IEEE Journal of Oceanic Engineering, 2011

In this paper, the context of several self-propelled, short-length cables, embedded with passive ... more In this paper, the context of several self-propelled, short-length cables, embedded with passive sensors for environ- mental diagnostics and swimming efficiently in formation over long duration and in shallow water, is considered. The basic problem of this volumetric diagnostic—namely, the low-speed motion control of a short-length, neutrally buoyant cable—is examined. More specifically, the constant-rate, circular turning of a 7-m-long cable

Synchronization of Animal-Inspired Multiple High-Lift Fins in an Underwater Vehicle Using Olivo–Cerebellar Dynamics

IEEE Journal of Oceanic Engineering, 2008

The development of neuroscience-based control methodologies and their integration with the high-l... more The development of neuroscience-based control methodologies and their integration with the high-lift unsteady hydrodynamics of control surfaces inspired by swimming and flying animals are the subjects of this paper. A biology-inspired rigid autonomous undersea vehicle called the biorobotic autonomous undersea vehicle (BAUV) has been developed at the Naval Undersea Warfare Center (NUWC), Newport, RI. The BAUV is equipped with six simultaneously rolling and pitching fins for generating large unsteady control forces for performing agile maneuvers. First, as an exploratory example, we introduce the van der Pol oscillator as an oscillatory controller for the BAUV and we describe experiments performed to examine the fin forces (thrust and lift) and electric power requirement, and to demonstrate the effectiveness of the oscillator's limit cycle property for disturbance rejection effectiveness. We then describe a BAUV control system that includes six inferior-olive (IO) neuron models for control of the pitch and roll motion of the six foils. These IO neurons exhibit limit cycle oscillation (LCO). For control of the BAUV, these IO neurons must oscillate in synchronism with specific relative phases. We present here four feedback linearizing control systems of varying complexity for control of the relative phases of the IO neurons. It is shown that each of the IO control systems accomplishes asymptotic regulation of the phases and thus enables the foils to produce the required control forces. The first controller has a global synchronization property, but the remaining controllers accomplish local synchronization. We present simulation results for tracking piecewise, time-varying phase angle commands as well as experimental results for control of the BAUV by IO neurons. The results show that with appropriate phasing of the fins, an optimal graceful gait of the BAUV is achieved where no untoward force or moment is present. An analog hardware version of the local controller with a cluster of six IO neurons has also been built, which allows five of the signals to rapidly synchronize to the reference, with or without prescribed phase shift, much like in the simulations. The designed controllers Manuscript

format_quoteThe IO control systems enable asymptotic regulation of phases for the BAUV, achieving local and global synchronization for effective maneuverability.format_quote

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Biorobotic adhesion in water using suction cups

Bioinspiration & Biomimetics, 2008

Echeneid fish, limpets and octopi use suction cups for underwater adhesion. When echeneid fish us... more Echeneid fish, limpets and octopi use suction cups for underwater adhesion. When echeneid fish use suckers to &#39;hitch a ride&#39; on sharks (which have riblet-patterned skins), the apparent absence of any pump or plumbing may be an advantage over biorobotic suction cups. An intriguing question is: How do they achieve seemingly persistent leak-free contact at low energy cost over rough surfaces? The design features of their suckers are explored in a biorobotic context of adhesion in water over rough surfaces. We have carried out experiments to compare the release force and tenacity of man-made suction cups with those reported for limpets and echeneid fish. Applied tensile and shear release forces were monotonically increased until release. The effects of cup size and type, host surface roughness, curvature and liquid surface tension have been examined. The flow of water in the sharkskin-like host surface roughness has been characterized. The average tenacity is 5.28 N cm(-2) (sigma = 0.53 N cm(-2), N = 37) in the sub-ambient pressure range of 14.6-49.0 kPa, in man-made cups for monotonically increasing applied release force. The tenacity is lower for harmonically oscillating release forces. The dynamic structural interactions between the suction cup and the oscillating applied forcing are discussed. Inspired by the matching of sharkskin riblet topology in echeneid fish suckers, it was found that biorobotic sealed contact over rough surfaces is also feasible when the suction cup makes a negative copy of the rough host surface. However, for protracted, persistent contact, the negative topology would have to be maintained by active means. Energy has to be spent to maintain the negative host roughness topology to minute detail, and protracted hitch-riding on sharks for feeding may not be free for echeneid fish. Further work is needed on the mechanism and efficiency of the densely populated tiny actuators in the fish suckers that maintain leak-proof contact with minimal energy cost and the feasibility of their biorobotic replication.

Henry Leinhos

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