Marius Pruessner

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.

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

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.

Thrust magnitude and efficiency studies for multiple robotic flapping fins

The development of multiple generations of robotic flapping pectoral fins has warranted a closer study of the relative thrusts and efficiencies exhibited by these fins. This paper describes the differences between the various fins - including stroke frequency, stroke amplitude, aspect ratio, and effective angle of attack - and investigates the effects these differences have on thrust generation and propulsive efficiency. Drawing from and building on previous fin results, both computational fluid dynamics (CFD) simulation results and experimental data are used to evaluate the thrust, power draw, and efficiency, and to find useful relationships between these values and parameters such as Strouhal number and advance ratio. This analysis has implication for future fin design and development of reduced order models for flapping propulsion mechanisms.

Bioinspired Design Process for an Underwater Flying and Hovering Vehicle

l We review here the results obtained during the past several years in a series of computational and experimental investigations aimed at understanding the origin of high-force production in the flapping wings of insects and the flapping and deforming fins of fish and the incorporation of that information into bioinspired vehicle designs. We summarize the results obtained on pectoral fin force production, flapping and deforming fin design, and the emulation of fish pectoral fin swimming in unmanned vehicles. In particular, we discuss the main results from the computational investigations of pectoral fin force production for a particular coral reef fish, the bird wrasse (Gomphosus varius), whose impressive underwater flight and hovering performance matches our vehicle mission requirements. We describe the tradeoffs made between performance and produceability during the bio-inspired design of an actively controlled curvature pectoral fin and the incorporation of it into two underwater flight vehicles: a two-fin swimming version and four-fin swimming version. We describe the unique computational approach taken throughout the fin and vehicle design process for relating fin deformation time-histories to specified desired vehicle dynamic behaviors. We describe the development of the vehicle controller, including hardware implementation, using actuation of the multiple deforming flapping fins as the only means of propulsion and control. Finally, we review the comparisons made to date between four-fin vehicle experimental trajectory measurements and controller simulation predictions and discuss the incorporation of those comparisons into the controller design.

Optical Signatures and Detection Strategy for a Finned Bioinspired Unmanned Undersea Vehicle

The surface expressions for a submerged finned bioinspired unmanned underwater vehicle (UUV) were examined using VNIR and longwave infrared sensors as the system maneuvered in laboratory and field environments. Laboratory experiments revealed that the eddies generated by the flapping of the finned propulsion and attitude control system initially appeared as discrete thermal boils on the water surface. As these boils evolved, expanded, and merged into one another, two parallel thermal tracks were observed. The tracks cross-linked forming a single thermal swath or footprint behind the trajectory of the vehicle. Similar thermal disruptions were observed when experiments were performed in an uncontrolled harbor environment under daytime and nighttime lighting conditions. Estimates for the background clutter, system signal, and detection statistic were generated using probabilistic models to demonstrate the feasibility of extracting signals from complex environments in both laboratory and harbor experiments. Performance of the detection model was presented in the form of receiver operating characteristic curves. Results clearly demonstrate that we can achieve > 99% probability of detecting the presence of the UUV with a very low probability of false alarm (< 0.005%) in a real harbor environment, where we estimate

Swimming performance of a hybrid unmanned air-underwater vehicle

\text{signal-to-noise ratio}=21.5

Maneuvering performance of a four-fin bio-inspired UUV

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