Jason D. Geder

Platinum-Paper Micromotors: An Urchin-like Nanohybrid Catalyst for Green Monopropellant Bubble-Thrusters

Platinum nanourchins supported on microfibrilated cellulose films (MFC) were fabricated and evaluated as hydrogen peroxide catalysts for small-scale, autonomous underwater vehicle (AUV) propulsion systems. The catalytic substrate was synthesized through the reduction of chloroplatinic acid to create a thick film of Pt coral-like microstructures coated with Pt urchin-like nanowires that are arrayed in three dimensions on a two-dimensional MFC film. This organic/inorganic nanohybrid displays high catalytic ability (reduced activation energy of 50-63% over conventional materials and 13-19% for similar Pt nanoparticle-based structures) during hydrogen peroxide (H2O2) decomposition as well as sufficient propulsive thrust (>0.5 N) from reagent grade H2O2 (30% w/w) fuel within a small underwater reaction vessel. The results demonstrate that these layered nanohybrid sheets are robust and catalytically effective for green, H2O2-based micro-AUV propulsion where the storage and handling of highly explosive, toxic fuels are prohibitive due to size-requirements, cost limitations, and close person-to-machine contact.

High Aspect Ratio Carbon Nanotube Membranes Decorated with Pt Nanoparticle Urchins for Micro Underwater Vehicle Propulsion via H2O2 Decomposition

The utility of unmanned micro underwater vehicles (MUVs) is paramount for exploring confined spaces, but their spatial agility is often impaired when maneuvers require burst-propulsion. Herein we develop high-aspect ratio (150:1), multiwalled carbon nanotube microarray membranes (CNT-MMs) for propulsive, MUV thrust generation by the decomposition of hydrogen peroxide (H2O2). The CNT-MMs are grown via chemical vapor deposition with diamond shaped pores (nominal diagonal dimensions of 4.5 × 9.0 μm) and subsequently decorated with urchin-like, platinum (Pt) nanoparticles via a facile, electroless, chemical deposition process. The Pt-CNT-MMs display robust, high catalytic ability with an effective activation energy of 26.96 kJ mol(-1) capable of producing a thrust of 0.209 ± 0.049 N from 50% [w/w] H2O2 decomposition within a compact reaction chamber of eight Pt-CNT-MMs in series.

Fuzzy logic PID based control design and performance for a pectoral fin propelled unmanned underwater vehicle

This paper describes the modeling, simulation, and control of a UUV in six degree-of-freedom (6-DOF) motion using two NRL actively controlled-curvature fins. Computational fluid dynamic (CFD) analysis and experimental results are used in modeling the fin as part of the 6-DOF vehicle model. A fuzzy logic proportional-integral-derivative (PID) based control system has been developed to smoothly transition between preprogrammed sets of fin kinematics in order to create a stable and highly maneuverable UUV. Two different approaches to a fuzzy logic PID controller are analyzed: weighted gait combination (WGC), and modification of mean bulk angle bias (MBAB). Advantages and disadvantages of both methods at the vehicle level are discussed. Simulation results show desirable system performance over a wide range of maneuvers.

Computations of Flapping Flow Propulsion for Unmanned Underwater Vehicle Design

Three-dimensional unsteady computations of the flow past a flapping and deforming fin are performed. The computed unsteady lift and thrust force-time histories are validated with experimental data and are in good agreement. Several fin parametric studies are performed for a notional unmanned underwater vehicle. The parametric studies investigated the force production of the fin as a function of varying the flexibility, the bulk amplitude of fin rotation, the vehicle speed, and the fin stroke bias angle. The results of these simulations are used to evaluate the hydrodynamic performance of the vehicle and to support controller development. Computations are also performed to map out the hydrodynamic characteristics of a new test vehicle, designed and built at Naval Research Laboratory to demonstrate the hovering and low-speed maneuvering performance of a set of actively controlled curvature fins.

Design, Development, and Testing of Flapping Fins with Actively Controlled Curvature for an Unmanned Underwater Vehicle

This paper describes the design, construction, and testing of a biomimetic pectoral (side) fin with actively controlled curvature for UUV propulsion. It also describes the development of a test UUV and the design of a fin control system for vertical plane motion. A 3D unsteady computational fluid dynamics (CFD) analysis has been carried out to computationally optimize the fin design including a full study of the primary design parameters. The fin has been constructed and it can reproduce any specified deformation time-history. The full dynamics of the proposed vehicle have been modeled and the forces produced by the flapping fins computed. Finally, the stability of motion in the vertical plane has been analyzed and a control system has been designed.

Robotic pectoral fin thrust vectoring using weighted gait combinations

A method was devised to vector propulsion of a robotic pectoral fin by means of actively controlling fin surface curvature. Separate flapping fin gaits were designed to maximize thrust for each of three different thrust vectors: forward, reverse, and lift. By using weighted combinations of these three pre-determined main gaits, new intermediate hybrid gaits for any desired propulsion vector can be created with smooth transitioning between these gaits. This weighted gait combination WGC method is applicable to other difficult-to-model actuators. Both 3D unsteady computational fluid dynamics CFD and experimental results are presented.

FOUR-FIN BIO-INSPIRED UUV: MODELING AND CONTROL SOLUTIONS

This paper describes the modeling and control development of a bio-inspired unmanned underwater vehicle (UUV) propelled by four pectoral fins. Based on both computational fluid dynamics (CFD) and experimental fin data, we develop a UUV model that focuses on an accurate representation of the fin-generated forces. Models of these forces span a range of controllable fin parameters, as well as take into account leading-trailing fin interactions and free stream flow speeds. The vehicle model is validated by comparing open-loop simulated responses with experimentally measured responses to identical fin inputs. Closed-loop control algorithms, which command changes in fin kinematics, are tested on the vehicle. Comparison of experimental and simulation results for various maneuvers validates the fin and vehicle models, and demonstrates the precise maneuvering capabilities enabled by the actively controlled curvature pectoral fins.Copyright

Modeling and Control Design for a Flapping-Wing Nano Air Vehicle

A full six-degree-of-freedom vehicle model is constructed for a flapping-wing nano air vehicle (NAV) which includes components for the body, wings, sensors, and unique shape memory alloy (SMA) driven actuator mechanisms. The design of these actuator mechanisms and the link between the SMAs and wing kinematics is described. Algorithms for sensory feedback control of the vehicle dynamics are designed and implemented in simulation. The outputs of four control modules command changes in the wing stroke amplitude, mean position, and plane angle. An extended Kalman filter is developed to improve attitude estimation and stabilize the NAV. Vehicle responses to hover, forward flight and turning commands are assessed and desirable performance is achieved.

Scaling studies for an actively controlled curvature robotic pectoral fin

Scaling studies for an actively controlled curvature robotic pectoral fin are presented in detail. Design, development, and analysis of the fin are conducted using a combination of computational fluid dynamics tools and experimental tests. Results include a Generation 2 (Gen2) fin design with approximately 3x more surface area and a slightly larger aspect ratio compared with our Generation 1 (Gen1) version. The Gen2 fin demonstrates 9x more thrust production than the Gen1 fin, validating the computational studies. Additionally, changes to the structural design of the ribs and actuation of the rib angles leads to a power savings and a more efficient fin.

Development of a robotic fin for hydrodynamic propulsion and aerodynamic control

An unmanned vehicle is being developed for highspeed aerial ingress to a target shallow water environment after which it will transition to underwater low-speed operations. This paper describes the design and analysis of a bio-inspired robotic fin for use as an underwater propulsion and control mechanism, and the effect this fin has on the aerodynamic characteristics of the air-deployed vehicle platform. Building on previous fin research, both computational fluid dynamics (CFD) simulation results and experimental data are used to evaluate the hydrodynamic thrust of a flapping fin, as well as the aerodynamic lift of a static fin. This analysis validates the fin design for use on a hybrid air-underwater vehicle.